I second what Cleeve said. To answer your last question, for 190$CDN I don't believe there's a faster card than the 7900GS. The lowest priced X1950Pro is at 207$ at directcanada.com and is about the same value. I don't think it beats the 7900GT though.
Hmm, I can't comment on Canadian pricing, but I'd definately take a new X1950 pro for $207 before I'd buy a used 7900GT for $200.
And if a X1950 pro is $207 now, chances are a better deal or better card for the money would come along before he buys his other parts. Of course, it could go the other way too if supply dries up, but more often than not you'll get more for your money waiting until you have a system to put the card in than stocking a card on your shelf for a month. (trust me I know this all too well. )
Just a side note, the cheapest X1950 ROs I've seen in canada were $250+, I didn't know you could get them for $207. That makes things a bit more complicated, although you'll be paying tax on the PRO you will have a warranty which is good...