Question about GTA 4 graphics settings

[Darkstar One]

So I just got around to buying and installing this today.

The system I'm playing it on is an i7-920, 6GB of DDR3, with a 512MB Radeon HD4850.  However, either the drivers/card/MB/whatever has some kind of feature where in addition to the video card's 512MB of onboard RAM, it can draw on unused system memory, up to 3GB worth.
Don't ask me how it works.  PLEASE.  My brain cells will melt.

Anyway, the system has run anything I've thrown at it at 1920 by 1080 with good framerates.  Crysis?  No problem.

So imagine my surprise when I installed GTA 4, ran it for the first time, and the graphics auto-adjust to LOW MEDIUM--and won't let me increase them!  (Draw Distance, etc, set to around 25%)/
So I do a little research online, find out how to unlock the graphics, and crank everything all the way up, to the point where at 1920 by 1080 it's telling me it's using almost 1.5GB of graphics memory.
I run the benchmark, and I get 35 FPS.

Is there any hardware or software related reason anyone knows of why I would NOT want to crank the graphics up?

[Darkstar One]

C'mon, someone here must still be playing this and know the answer

[hitbyambulance]

i bought a secondhand copy of the Xbox 360 version just so i wouldn't have to deal with this very issue (ok, and the DRM as well.) sorry...

[frost]

nice computer.  is that from cyberpowerpc?  anyway, i can't really help you out, as i'm playing gta4 on a amd 3800 X2, 2 gb of ram, and an 8800gts older card, so my settings are on the lower end as well.