Looks like the only difference between these two cards is a 100MHz difference in core clock:
http://www.overclockers.co.uk/showproduct.php?prodid=GX-287-AS&groupid=701&catid=56&subcat=1673
http://www.overclockers.co.uk/showproduct.php?prodid=GX-275-AS&groupid=701&catid=56&subcat=1673
Am I missing something here? Wouldn't the 800MHz version easily clock up to 900MHz? I suppose your overall overclocking limit might be lower with the 800Mhz version?
http://www.overclockers.co.uk/showproduct.php?prodid=GX-287-AS&groupid=701&catid=56&subcat=1673
http://www.overclockers.co.uk/showproduct.php?prodid=GX-275-AS&groupid=701&catid=56&subcat=1673
Am I missing something here? Wouldn't the 800MHz version easily clock up to 900MHz? I suppose your overall overclocking limit might be lower with the 800Mhz version?