Just to let you know, 8 grand could easily grab you a 328, or a 3.0L M3 with a bit higher mileage if you look around. (10g could very easily snag you a 3.0)
I wouldnt spend more than 5-6 grand on a 325, thats just me though. It also depends on the condition and what the car already has on it, but i wouldnt drop more than 6 grand on a stock 325. You could spend more than that though.. if its low low mileage, and cooling system problems have already been dealt with.
An example of how low 325's are getting down these days is how much i got my car for; i bought my car for 4500 with 124k on it. Recent clutch, and all preventative maintenance done. My car has a worn in interior, and a couple dings though.. but she still shines like a champ with a coat of wax.