torn between configurations, help please

im looking at buying a new gaming laptop, no more than $2500 though..i looked at HP and really like what they have to offer but i cant decide between 2 graphics cards, 2 procesor types and 2 ram options: one graphics card is the geforce 511mb 8600M GS the other is a 383 MB 8400M GS. the 2 ram configs are 2GB or 4GB. i didnt know if 4GB is a little overkill or not. as for the vid cards, ive never seen a 511mb or 383mb config in any video card, usually its all 128, 256 or 512. the processor i was looking at was either a 2.0ghz intel core 2 dup or 2.2 ghz core 2, i didnt know how much difference that extra .2 ghz would really make and its like $100 extra...so i guess im at a loss i have no clue what to get, i dont even know if these video cards are good or not. im also using this laptop for school and home entertainment so i dont want it to be solely for gaming, but since gaming obviously requires the most resources i figure i should list that as its primary function

i looked at dell but i sidelined them when i built the exact same laptop at HP's site for almost $1000 less...not to mention the dell had a 12" screen and a shitty video card, i think dell is FAR to over-priced but maybe i just wanst looking in the right laptop section (they only have like 30 different choices lol)

ok yea for some reason i was only looking at the xps laptops because i thought that was dells gaming line...thanks for the tips, the dell and the hp cost about the same so its a toss up, but your right the dell vid card is better..i looked at that Np5790 model, it was nice but i think id just prefer something name brand (such as dell or hp), im just a whore like that lol

one last question; whenever im seeing video cards now im seeing them listed as "UP TO 512MB OF SHARED MEMORY!!!" then in tiny tiny fine print at the bottom of the page (only contains 128 mb of dedicated memory)

whats all that mean? when a game lists its system requirements it says something like "requires 256mb graphics card or higher", it doesnt specify shared or dedicated... so would a graphics card with 128mb dedicated and up to 512 shared be able to support a game that requires 256? and forgive me if thats the most noob question youve seen but i dont know a lot about this stuff as you can tell