The NVidia 2XX range of cards is now obsolete, you will only pick them up second hand, unless there is a local dealer who had a shedful of them at EOL time. The other major factor is power drain, running both a 260 and 220 will eat electricity compared to running one modern card. I'd dispose of the 220 if Santa comes along, and just run the modern card. The latter will way outperform the 220 & 260 combined.
At that comparitive level of card in the 2XX range, you now have a choice between the NVidia 460 or 470, and AMDs new 6850 or 6870. In terms of bang for your buck, there is no contest, AMD cards will get it every time. NVidia reduced their 460 & 470 prices about 10 days ago, as they were being taken down by the AMD 5850s, and would not stand up to the new AMD 68XX cards.
All four cards are close to each other now in broad terms of price, but the AMD cards still stand out as more powerful. Be aware that the 68XX cards do not support Double Precision, so if you want to crunch for a DP project, you will either have to go NVidia 460 or 470, or you could go for an AMD 5850, in the older AMD 58XX range, which still take down the 460 & 470s. The prices of 5850s will drop shortly as dealer clear stocks with 68XX coming out, so could be a good buy for you.
I personally would say it boils down to:
AMD 5850 or AMD 6850. The former you should get at a great knock down price shortly, and despite being 3 years older in design than the NVidia 4XX, will still take down the 460 & 470. If Santa will stretch to it, a 6850 would be a real good buy and stand you in good sted for years, just be aware of no DP in the 68XX range..
Guru3D 6850 review and benchmark comparisons is a good indicator for you on compartive performance of the cards in question, and the review gives a good detailed look at the 6850, which they are very impressed with. Guru3D is always a good site to bookmark for hardware searching and buying help, excellent non biased reviews.
If those cards are too high for Santa, there is no contest as NVidia do not have cards in the next range down that can compete with the 5830 (has DP capability) or the 5770 (no DP capability).
Guru3d 5830 review
Regards
Zy