Have a look at one of this Dell XPS - XPS 210 fits your budget and it's pretty decent machine: it allows upto
- Intel® CoreTM 2 Duo Processor E6700 (4MB L2 Cache,2.66GHz,1066)
- and 4GB12 Dual-Channel DDR25 SDRAM (533MHz, 2 or 4 DIMMs).