Well multi-monitors suggests many programs. So you'll probably want a decent amount of RAM, and if it's a crazy amount of monitors, maybe a couple of enterprise class cards running in SLI to support them all.
The OP inferred he was some what tech savvy. He will talk the clients into it. Plus I would not enjoyed the build as much if I had gone over budget more than the price of a candy bar. lol
I won't go with a Samsung 840 EVO Solid State Drive, it's a consumer part and has a higher failure rate than say the Samsung 840 PRO edition. I'd recommend an Intel 530 Series 120GB Solid State Drive, must higher reliability rate, which you'll want, even 5-10 minutes of down time could cost $1,000s on the stock market, let alone a couple weeks to get a replacement.