The Sparkle/Fortron 550w recommended is the cheapest such PSU I know of that can be considered not skimping in some way. It's not geared for absolute silence and is not the most efficient design by today's standards, but it will do rated power and last and last and last. The modular capabilities of the Ultra do look good, but that's exactly what you're paying for with them - the Wintech made innards are average quality.
The Fortron AX500-A will also power that rig if you're looking to save a little more money - it's not a whole lot cheaper than the 550w PLG, but has a little more bling factor to it and a 120mm fan.
I'd suggest avoiding modulars entirely if you're on a tight budget. The better ones that are ok quality inside will probably set you back more than you want to spend. Right now, the only two modulars I like are the Seasonic made Antec Neo HE's and the Enermax Liberty line. I'd suggest no lower than 480w from either line for a P4 build.