Yeah Munky, I upgraded my whole computer, trying to optimize for ROM without paying too much.

I find that 4 gigs of RAM, a good video card with 512 MB RAM and a decent 3 gig single core processor helped a lot. I think the video is part of it... multiplayer we hypothesize that part of our lag problem at the end of turns is the sorting out of massive amount of AI moves, etc. We were on a Huge map and had to give up and are starting our next game on Large.
That reminds me I need to move a few things in my unloaded modules - static leader heads and no buildings graphics if I remember right. My computer is still the slow down one on the multiplayer games, but I love the farthest away and have the slowest net connection, so thinking that might be a big part of it.
We are not having a lot of trouble with crashes or OOS, but we also aren't getting into the modern age either. There's some custom modding going on messing with governments to make everything more interesting (harder if you ask me!) and we are running with Rev on atm having toned it down to let the AI have a lot less trouble with it and the humans a bit less. Our OOS tends to happen when someone first goes to war and starts a battle. Later battles seem less likely to cause this, but I haven't seen an OOS unless someone is at war (usually one or more of the players). Losing or taking a city often causes OOS.
Performance is an issue - this is the only real reason to play BTS and it can be a bummer when the game gets unplayable due to performance issues. I can't really justify getting a computer like Zapparas just to play CIV!