Your system would probably boot, but you might have some power related problems. I have a similar system, and I have had problems with my CDBurner and over 128 mb RAM. I got post errors until I started disconnecting, but the problem went away when I switched the PS to 400 watt. The power demand from your system would wear away at a 300 watt PS. I would recommend a 400 watt PS for any system over 1.5 GHZ.
I have posted a link for a 400 watt PS for 15 bucks. I have bought from this company before. Their products are rock solid and customer support is amazing.