Man, those cards used to be the shit. Seemed like everyone and their cousins were mining on those.
I still do. I have tons of them. I have half of them mining BTC, and the other half mining LTC. They aren't as great mining LTC as they were BTC. Might be upgrading to 7850s soon-ish.
That's pretty much what I'm doing & why I'm ditching the 5830's. I'd still keep 'em since GPU mining will still be profitable for at least one more difficulty cycle (barring a collapse in the exchange rate) & most likely two or even three (at my 6.8c or so elec).... but right now I'm doing the whole mail in rebate + selling games coupons thing, replacing them with 7790's and 7850's when I see good deals on 'em. Reasoning is that if I take the time to do the MIR, the cards are already profit once they arrive at my doorstep (even after taking ebay fees).
I'm sure they won't drop in price as much as the 5830, 5850, 5870, & 5970.... the 7950's might be worth it too, but not going to touch a 7970 unless I see one for $300 or less..
example:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202004use the MIR on that and sell the games and you've got a card you payed $120 for.... $110-$115 if you put a little effort into selling the games
two good 7790's
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131490http://www.newegg.com/Product/Product.aspx?Item=N82E16814150667check how much they go for on eBay... if you do the MIR + sell those games, those are under $100