havent tried the demo yet :O
i struggled on team sabre but i was packing an AMD 1.4 GHz, since i have upgraded i have no probs on any games (inc FarCry).
the 4200 is a great card because it performs great, u can overclock it and it is dirt cheap. performance increases very well with faster processors so is a good choice.
you will pretty much all cards need a fan though :/ and a silent cooler :
http://www.zalman.co.kr/english/product/ZM80C-HP.htm will cost about £25