IMO well worth taking a look on the Overclockers uk site:
http://www.overclockers.co.uk/productlist.php?groupid=701&catid=339&subid=791
Bundles £240 - £430 (Mobo, Memory and CPU)
Add on your other requirements Graphics, Sound (if not onboard), Optical Drive etc.
Worthwhile giving them a call before ordering to check your components all compatible. I have used this company several times and been very pleased with service and speed of delivery
EDIT: What is your current PC spec e.g. Mobo, Memory, Graphics etc. Suspect possible bottleneck could be due to the amount of system RAM you have installed if less than 512MB- also look at video RAM requirements
Basic Spec rec. by Adobe
# Intel® Pentium® 4, Intel Centrino®, Intel Xeon®, or Intel Core™ Duo (or compatible) processor
# Microsoft® Windows® XP with Service Pack 2 or Windows Vista™ Home Premium, Business, Ultimate, or Enterprise (certified for 32-bit editions)
# 512MB of RAM
# 64MB of video RAM
# 1GB of available hard-disk space (additional free space required during installation)
# 1,024x768 monitor resolution with 16-bit video card