If your Looking to use a keyboard and mouse in any game on the PS3 look into making a XIM. Its the most configurable option out there. I just made mine and I'm loving it.
If you dont care about if its a fat PS3 or a slim. You can get a 80gb and upgrade the HD for about the same price as the 250. I have about 4 games installed and 20 ps3 games, Im using about 60gb of space on my fat PS3 80. I also stream all my music and videos.
I never had a problem with my wireless, although I thought it was slow. I just got a cheap router and put DDWRT on it. It ended up being faster and i got a 5 port bridge down stairs:cool:.