512 mb vs 1 gb

im a gamer and in the process of building a system right now...would there be a noticable performance increase between 512 mb pc2700 ddrram and 1 gb?

Yes it runs slower

Depends on your OS m8. If you're using 95/98/ME there's no point as it won't utilise the extra memory fully. 2000 or XP will, but unless you're doing a lot of video-editing or graphics work there's no real need. No gaming system currently requires more than 512Mb, 256Mb will often be quite sufficient.