HELP! Onboard Vid vs. Old card vs. New Card vs. $$$ New Card, WHICH 1?

So after researching a lot from the forums and reviews, I went ahead and bought most of the components for a completely new system yesterday (3/11) from newegg and will use what I already have as well.
I already have:
Case: 18.5"x17.5"x7.5" ATX Clear Acrylic Case
PSU: Corsair TX650W 650 Watt Power Supply
Burner: LG 22x? DVD Drive
Old Vid: Abit RX700 Pro-256PCIE w/ 256MB GDDR3 memory
Lots of various screws/cables/adapters/cards/fans etc.
The rest of my old system I plan on selling (mobo/cpu etc) so I won't list that stuff...

New stuff:
Mobo: Biostar Tforce TA790GX 128M w/ ATI Radeon HD 3300 onboard video
CPU: AMD Phenom II X3 720 Black AM3 2.8Ghz
Memory: 2x2Gigs OCZ DDR2 1066 PC2 8500 240-Pin
HDD: Western Digital 640GB Black SATA 3.0Gb/s OEM (hope it works!)
Cooler: Xigmatek HDT-S1283 120mm Rifle

So my question is for what video to use. I had planned on using the onboard vid until I could save up another couple hundred to buy a nice new card (I liked the Gigabyte GV-R485MC-1GI Radeon HD 4850 1Gb 256-bit GDDR3 PCIe 2.0 x16 for $170, since it has no fan and I like quiet). But newegg has a one day special, so I need advice quickly plz, on this card:
Powercolor AX3650 512MD2 Radeon HD 3650 512MB 128-bit GDDR2 PCIe 2.0 x16 for $40.
So should I just stick with the onboard video? or use my old X700? or buy the deal on the Radeon 3650? or just wait and buy the GB Radeon 4850?
I like to game, and have built this computer to try and update so that I can play any game on near or highest settings. I also want to know if I should get a new monitor to game on, but I also plan on hooking this system up to my 47" LG 1080p HDTV, could I just use that to game on?
Ok, so I might be forgetting some info, if I am just ask, but I want to go ahead and post this to get as much feedback today as possible, THANKS IN ADVANCE ALL!