There was once a CVAC - Heartland challenge, and it was grand. While the CVAC is still trying to return to their former glory, the Heartland is very strong in DII Iba.
I'm going to call "Major conferences" conferences with 6 or more humans with top 10 conference RPIs.
Major Conferences
Heartland
It's an interesting season in the Heartland, where 11 schools are really good, but nobody is great. San Anto historical powers IW and St. Mary's aren't running things like they used to, though they are still in the hunt. #10 Valdosta St. might somehow have the best squad in the conference especially due to their two starting bigs. Amazing turnaround from a ridiculous 54 game losing streak the last 2 seasons. Watch out for St. Mary's - they have the #2 SOS as the Yarnell invitational kind of beat them up, so they are much better than their 11-8 record. #15 Montevallo looks really good too - with one of the best DII small forwards in Fretwell.
Peach Belt
Lander is better than everyone else. Lander and N. Florida (and maybe AASU or Kennesaw) could ensure 2 potential final four teams from the Peach. While the Heartland is the conference with easily the most competitive depth, the Peach has probably the best top-end talent.
Great Lakes Valley
#9 Wisconsin Parkside steamrolled through conference after a killer OOC schedule that featured taking Lander to OT and losing to Kennsaw by 1. Needless to say, that's a scary team. They're as absurdly athletic as every other Parkside squad. I remember recruiting Yazzie with Longwood, he's doing well as a WP starter. #14 Bellarmine might not have the greenhawks magic, but they seem to have a fine coach leading them on another deep run. #20 S. Indiana looked stronger in Non-conference than in conference, but they are no joke as well. Mercyhurst has an ugly overall record, but they've played a ton of good teams, and could make a lot of postseason noise.
CVAC
#6 Pfieffer is very very good. Zorzii has built a strong team first built by detfirecat (now at Mount Olive) that has a great 1-2 perimeter/post combo in the starting lineup in Hugh and Mayer. Nobody else is ranked, but there are 7 teams that could make the NT, and everyone else is pretty good as well. There's going to be a lot of 7 to 14 NT seeds coming out of the young CVAC that others won't want to play. The other three schools making the most noise are Anderson, Erksine, and Longwood. Perennial doormat Anderson has made an amazing turnaround, but their schedule has been sort of weak Erksine has the best SF in DII most likely. Longwood might have one of the best starting frontcourts in DII, but very limited depth due to youth.
WVIAC
boclaird is a fixture at #7 Concord, being DII Iba's premier Fastbreak/press squad for a long time now. This might be one of his best teams, scoring a whopping 96 PPG with a strong 24 SOS. They could make a very deep NT run with that depth. Glenville St. is maybe playing above their talent level right now, but they are 9-0 in conference, so they can't be ignored. Ohio Valley has 2 solid starting guards and they should be in the NT.
Northern Sun
When the hell did coaches move to the northern sun? New Mexico Highlands is one of the most fun teams in DII, scoring a ton of points with a ton of depth. They came out of nowhere to win the NT a few seasons back, and are probably 1 season away from a similar run. Jtreeves has been at Wayne St. since the beginning of time,it seems. They are talented as always, and can win a few games in the NT, but most likely won't make a super deep run. Nebraska Kearney doesn't suck anymore, which is cool.
Best of the rest
Bvb and #2 Dominican are quite possibly Lander's biggest challengers. I don't know how they convinced Waggoner and Bookout to go the DII route - they could start for a lot of d1 squads. They played an insane OOC schedule and went 9-1, with their only loss to.....you guessed it......Lander.
#3 CSU Los Angeles is scary that they're this good with no seniors. They should be dominiating DII next season along with New Mexico Highlands. They're still in line for a 1 or 2 seed in the NT. They play stifling defense, and they can run as well.
Count #5 Bowie St. on the list of teams that "only lost to Lander". Their schedule in OOC play was decent enough, and it's nice to see Bowie St. back on the radar, and they've won 2 titles in the last 8 seasons, so an 18-1 Bowie St. team could really be tough.
#8 UC Colorado Springs might have the best starting guard duo in the country. It took them OT to beat a few middle-of-the-road squads, but they only have 2 losses, and they went 8-2 during a legit OOC schedule..
#11 Bentley just had their biggest win of the season over #19 Lemoyne. They're pretty good for a team that refuses to attempt three pointers.
#12 St. Cloud St. is 20-0. They have played nobody. They have one guard that is ridiculously good. This is a really hard team to assess, but they're 20-0, so they matter.
#13 West Georgia has 5 seniors, and made the elite 8 last season. 4 of their 5 starters score in double figures, (the other guy just runs around and sets picks, i guess), so they have great balance and experience in their starting lineup. I like this team. Despite no impressive wins, they could be a squad that comes out of nowhere and ends up in the final 4.
Super early final 4 picks - Lander, Dominican, N. Florida, Wisconsin Parkside
Elite 8 - Pfieffer, NM Highlands, West Georgia, Concord
Am I missing anyone? Any sleeper teams that didn't get a mention?