First, to your specific question:
the strings on one of my basses are higher than i would like. i check the neck and the amount of relief seems pretty good....
So yes, I'd lower the saddles and see what I get. Your concern is action, saddles adjust your action. If you then say "I can't get the action where I want it without buzzing" THEN you might start over with a full start-to-finish setup making sure everything is optimally set. Start here:
http://www.talkbass.com/forum/f18/all-basic-setup-questions-answered-here-125382/
Not with Q&A -- if you start with a structured approach from a professional shop/business, you will have a better basis to view the inevitable back and forth these threads inspire. They're GOOD back-and-forths, but you should start with an understanding of the basic process.
in general, when lowering strings at the bridge, in order to get lowest possible action, would i want relief in the neck or a virtually straight neck
You want consistent, clear tone across the board. The nut, relief, bridge, and frets, strings and your technique are all going to play a role. The "general rule" I think most follow is to go for very very little relief. But once you start tweaking the relief, you probably should give some thought to everything else to make sure that THEY are set optimally as well to give you consistent clear tone across the fretboard.
To the relief concepts so far -- I never take the strings off when adjusting the truss, and have never had a problem. I only recently pre-stressed a neck to adjust the truss, but in that case only so I could experiment with some very small adjustments and to try to see if I could get less of an "acclimation" change over night. For my Sterling, and for the various Fender Js I've owned, I just adjust the nut. The MIAs (and my Sterling) had no acclimation shifting, my MIM ALWAYS changed more overnight than at the time of the adjustment.
Good luck!!
ltt