What should I upgrade to?

Hi, I'm new to this forum, and I need some help in choosing some upgrades for my computer, in particular my processor.

I've downloaded CPU-Z to get some information on my motherboard etc. to see which processors will be suitable, and to be honest I am very in the dark about components like motherboards, processors and power supplies (like how big the wattage of my PSU has to be to support the new processor). I have been looking at a certain processor (because I want relatively cheap components) which is the AMD Phenom II X3 710 Socket AM2+ Processor which has a clock speed of 2.6GHz, and also the AMD Phenom 8650 triple core socket AM2+ processor with 2.3GHz clock (which is a bit cheaper)

CPU-Z Says my computer has:

- Dual core AMD Athlon 64 X2 5600+ at 2.8 GHz
- ASUSTeK Computer Inc. motherboard, model M2VTVM-VM890 which has a chipset VIA K8M890CE, southbridge VIA VT8237A, and LPCIO ITE IT8716
also, the BIOS is American Megatrends inc. version 0903 dated 5th sep 2007..

My computer also has (in case any info is needed)
1x 256mb (I think) nVidia GeForce 8600 GT
1x 500W PSU
1x WDC WD2500AAKS-00VYA0 ATA Device Hard Drive at 250GB
1x Optiarc DVD RW AD-5170A ATA Device DVD-Drive
1x Akasa card reader
1x Floppy Drive
2x 1GB DDR2 PC2-5300 Corsair RAM
Do I need to list anything else?

So, my main question is with my current motherboard, will any of them two processors work, and if so, do I need to buy a new power supply? I'd appreciate any help.

Thanks, Swain.

P.S - Sorry if this is in the wrong section.. and also sorry for lack of links - I'm unable to post URLs to images etc.