just started with bitcoins this week.

I have a small office with 10 desktops all running intel integrated graphics right now, their powersupplies are around 300w, i think three of them are half height card only.
I don't have the budget to get monster video cards for every machine looking around $300 total to get started, should I?

1. Get older ~$50 radeons for a few just to get these systems up and hashing? (used radeon 4850's from ebay?) -- 6 of these would consume approx 600w and generate hopefully ~ 540MH/s. Anyone have these?

2. take the 300 bucks and just get something for my office machine, and do the others one at a time later. Maybe a Radeon 6950 with a new PSU? it would only pull maybe 300w (guessing) and ~300 MH/s?

3. get nothing because bitcoins will be worthless in a month? and I already pull in a steady 350 MW/h with the old/crap hardware i have floating around now. (2 x 8800gts-512mb, a 4870x2, a GTX 460se, my macbook pro 6670m when its sitting on my desk)

my only real requirements for the cards is they have decent bang/buck, and they dont have fans that sound like lawn mowers like my old 4870x2 does right now. 

just looking for ideas.

thanks,
jim