Hey, all. I'm planning components for my first homebuilt rig and I would like some feedback.

My primary curiosity is about the Power Supply. I'm currently looking at a 750w PSU, but wondering if I could step down and save some money if that is ridiculously over my needs.

Anyway, here's my setup as currently planned. Love to hear any and all thoughts/criticisms/recommendations. :-)

Case:
ENERMAX Uber Chakra ECA5001B Black Aluminum / Steel ATX Full Tower
http://www.newegg.com/Product/.....6811124121

PSU:
CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 http://www.newegg.com/Product/.....6817139006

Motherboard:
ASUS M4A78T-E AM3 AMD 790GX HDMI ATX AMD Motherboard
http://www.newegg.com/Product/.....6813131366

CPU:
AMD Phenom II X4 955 Black Edition Deneb 3.2GHz 4 x 512KB L2 Cache 6MB L3 Cache Socket AM3 125W Quad-Core
http://www.newegg.com/Product/.....6819103674

RAM:
OCZ Gold 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Low Voltage Desktop Memory
http://www.newegg.com/Product/.....6820227365

Graphics card:
XFX HD-489A-ZDFC Radeon HD 4890 1GB 256-bit GDDR5
http://www.newegg.com/Product/.....6814150359

Sound card:
Creative Sound Blaster X-Fi XtremeGamer 7.1
http://www.newegg.com/Product/.....6829102006

Hard Drive(s):
SAMSUNG F1 RAID Class HE103UJ 1TB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Hard Drive
http://www.newegg.com/Product/.....6822152119
&
Seagate ST3500641AS-RK 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive
http://www.newegg.com/Product/.....6822148221

Optical Drive(s):
SAMSUNG Black 22X DVD+R 8X DVD+RW 16X DVD+R DL 22X DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache IDE 22X DVD±R DVD Burner
http://www.newegg.com/Product/.....6827151175
&
LITE-ON Black 22X DVD+R IDE 22X DVD Writer
http://www.newegg.com/Product/.....6827106327

Monitor:
LG W2353V-PF Black 23" 2ms(GTG) HDMI Full HD 1080P Widescreen LCD Monitor 300 cd/m2 50000:1 w/ Smart Package
http://www.newegg.com/Product/.....6824005125

Speakers:
Logitech S-220 17 Watts 2.1 Multimedia Speaker System
http://www.newegg.com/Product/.....6836121014

Operating System:
Windows Vista Ultimate 64-bit
http://www.newegg.com/Product/.....6832116473

Other stuff:
Keyboard:
Saitek PZ30AU Black 104 Normal Keys 4 Function Keys USB Standard Eclipse Keyboard
http://www.newegg.com/Product/.....6823175103

Mouse:
Logitech G5 7 Buttons Tilt Wheel USB Wired Laser 2000 dpi Mouse
http://www.newegg.com/Product/.....6826104076

I'm trying to keep my total budget, including all the peripherals and bells and whistles, in the 1500-2000 range, and right now i'm coming in just shy of 1800.

Thanks for any wisdom you may be able to impart! I fully concede I'm pretty new at all this.

If you have that high a budget you might be better off looking at a Core i7 system. The benchmarks I have seen show it coming out on top of the AMD Phenom II.
If you get the i7 920 it reportedly over-clocks really well (though I haven't tried on mine yet).

I wouldn't say 750W is over the top. It is probably 100W over what you need but as PSU's degrade over time it is good to have it higher than you need to start with.