First build...please help!

I have purchased two well known brands of computers in the last few years and had bad luck with them both. Therefore, I am trying my hand at building my own. This computer will be used for internet and photo editing. No gaming. I plan on using some of my parts from my dead HP. Here is what I am looking at.

This is what I am looking to buy:
mobo asus a8n-e or
asus a8n-vm csm (if onbaord graphics are okay for photo editing)
cpu amd athlon 64 3200+ venice core
evga 6600gt card (if getting asua a8n-e mobo)
cooler master centurion case

Whay I already have:
hipro 300 psu
barracuda 200gig hdd
hynix pc3200 512mb ddr 400mhz ram
dvd/cd writer
dvd-rom

Here are my questions:
How does this setup look?
Are onboard graphics okay if photo editing?
Is my psu enough?
Will an ultra atx mobo fit in an atx mid tower?
I want add 512mb more ram. Should I add to the budget ram I have or just buy new ram altogether?

Thank you so much for the help. This is my first build, so please be kind.

 

i would up the power supply to about 450 watt personally . skimping on power can lead to instability. also look for at least 25 to 30 amps on the 12v rail. (should be listed on the side of the psu). since you arent ocing value ram should be great for your purposes . I would go with the 6600gt video (personal preference on my part though) as for the board fitting a mid tower case not sure on that hopefully someone can answer that for you.