Yer welcome..
I've never used Circle KB. Seems like they've been around a bit and I've not heard any horror stories, but ask them for their delivery time and some referrals. If you are getting custom work done, plan on it taking a while.
Slides are ok for Classic and currently are being used in NCOWS. There is some "rumbling" that they may be officailly outlawed, but I can't truly comment either way. NCOWS just finished a landmark meeting of the Congress and I expect there will be a complete report forthcoming. If NCOWS is your primary concern, then you might want to wait a bit, to see the results of this meeting.
Frankly, four shotgun loops is a case of too few and too many. You might look for a canvas shotgun belt, they are available for $50 and give you lots of flexibility.. I use mine often. Your rifle choice is a good one, in fact, I think there is a fairly good deal on Gunbroker for a SRC. I'd still suggest the cheap chinese SxS. If you are going to spend the $300+ for a EAA, you might as well look at a Libery or TTN for another hundred.
If you haven't checked out the advertisement forums make sure you do, here, at TFS and SASSnet.com
Adios,