Good idea but prefer if I can get by with just the new one.Most probably. I'd say nearly 100% certain. Worst case if not, replace your two older GDDR3 cards with newer ones for maximum performance... then sell your old ones on eBay.
What resolution are you driving? The VRAM really is for 3D and gaming so if you are using the monitors to trade, you shouldn't have any problems with incompatibility.
On a second note, just how many monitors are you running total?
1920x1200 on 24 inch monitors.
Using only for trading. No gaming.
Makes sense.Resolution won't be an issue. Only possible thing is that the GDDR5 and GDDR3 don't work together... which I think is highly unlikely considering they are the same model card. (You know in your computer if you have RAM of different speeds, the faster just dumbs down to the speed of the slower.)