as a word of advice I would refrain from double posting as it's not within forum etiquette. You should request your other post (here) to be closed by a mod by posting in it.
Originally posted by asaeed: is it the higher the memory clock, the better?
Usually yes, this is the case, however there are well performing cards that perform better (and have slower clock speeds) than porrly designed cards (that are faster clock speed that perform worse). It is really a case of what the card is being asked to do, and whether it is designed to do it.
Originally posted by asaeed: what is pixel pipelines? higher the better?
These are the parallel processig pipelines within a GPU of a graphics card. Again, usually the higher the pipeline count, the better the card.
With regards to your question, they are equally good cards, but i personally would recommend the X1950 Pro. It has double the memory bandwidth (256 bit rather than the 128 bit that the 2600 has), but is more expensive. It does give much better performances using a resolution of 1280x1024 and over, especially with AA applied.
Some may argue the HD2600 is better (statistically), but in a real world environment the X1950 Pro is a better card.
Personally I think you will be limited to choice by the graphics adapter type. The AGP is still holding on, but will inevitably die a death with multiple PCIe setups. I would probably save my money for a future system upgrade in the next 6 months.
