I did some research, and ended up with a plan to move forward, preserve options, and realize at least some benefit now.
I picked up a UA 710, Joe Meek ThreeQ, TC Helicon Voiceworks Plus, DBX 1066, and a pair of patchbays, XLR and 1/4" TRS. I am ordering a GAP Pre 1073 today.
That wil give me a selection of tube and non-tube preamps to use immediately, a transparent dynamics controller to just take the edge off peaks on the way in, and an effects processer that should double as an analog reverb unit for vocal headphone monitoring, and adigital effects processor via SPDIF for post processing.
(I also stumbled over a used MOTU 2408 w PCI card for $170, that will fit nicely into a supporting PC in either the tracking or control room, an unexpected bonus!)
That leaves a 1 rack unit space for future expansion in directions not yet considered, and a two unit half space that will probably end up filled with an Avalon M5 or V5, I haven't decided yet.
The M5 seems to be a better pre, while the V5 offers a good pre plus DI and reamp capabilities.
I'm not sure how well the rackmounts for the UA and Avalon will coexist, but they physically fit the space, and I hope mounting won't be too difficult.
Thomas and others, I appreciate the time you took to point me in the right direction, it made wading thru the infinite variables MUCH easier.
Thanks!