Not even the most avid Nvidia fanboy can deny the outstanding value you get with the Radeon R9 290. There is a slight trade-off, however, and that's the noise level of the 290. AMD's GPU gets hotter than Nvidia's at the same level of performance, and therefore requires more cooling which produces more noise. AMD had to boost the 290 in order to get that type of performance with fewer shader units than in the 290X.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips