As a follow up to this since its been a few months...
I actually decided on going with the Coherent 18 speakers instead of the 15s, and I put a deposit down on a pre-amp and amplifier combo the other day and decided to go with Aric Audio.
Preamp - Super 6SN7 Linestage
Amplifier - Super 2A3 SET
This set pretty much tops out my budget, but after speaking with another Coherent 18 owner who loves them, talking with Aric, and looking into reviews, they seem like a great choice.
Other than that, a major selling point for me is that they are made in the US. I'm not really a 'made in US' only buyer (clearly, given the Coherents are Canadian), but for tube amplifiers, I prefer for peace of mind when it comes to potential future repairs. I've read many horror stories about amplifiers made overseas and trying to get service done being not only a huge hassle, but expensive with shipping and long down time.
Going the separates route will also give me greater flexibility with amp experimentation in the future, should I want to try out different SET amplifiers, since it's often easier to come across stereo/mono amps versus integrated with SET.