Self directed IRA/Solo 401k providers

[Jim M.]

Here is my situation: I currently have a decent chunk of money in a few accounts from a former employer's retirement program.  They are 401a and 403b's.  The current custodian is TIAA.  I have not worked for this employer for one year, and could roll these accounts out to other custodian(s) if I wanted to. 

Here's the kicker: I am thinking about going back to work for that employer.  If I do, that money will be locked up at TIAA again.  So, I want to roll it out *before* I return to work for them.  Obviously, any money that I contribute in the future to the employer's plans will have to stay at TIAA, but I want to liberate the existing accounts before they get locked there again.

I want to transfer to a custodian that allows self-directed IRA or Solo-K. Solo-K would be my preference since this will allow me to avoid tripping the pro-rata rule when I make my backdoor Roth contribution/conversion every year.

My question is, which self-directed provider to use??  BP has a nice article at https://www.biggerpockets.com/rei/self-directed-ir... which lists 58 (!) providers.  I don't have time to investigate that many companies and would like to pare down the list to no more than a dozen before I start doing my due diligence on each one.  I would like a custodian that allows checkbook control which would make real estate investing from the account much easier.  Other than that, lower fees are better than higher ones, of course, and....what else should I look for in making comparisons??

Thanks in advance! :)