I prefer Pentium CPU's for their added insurance against meltdown.
Check out the article Tom's Hardware did awhile back on the Barton and Thoroughbred cores versus the PIII Coppermine and the 2.4C processors...the AMD chips fried within two seconds if the heatsink was displaced; the Intel procs just throttled back and cotinued to run with no damage; both AMD procs died horrible, nasty deaths.
I know AMD64 chips are better performers when running some single apps, like gaming, and most of the pure gaming rigs I make include them rather than Intel procs. And they cost less for actual processing power.
But most customers get Pentiums, even though they cost a bit more. The reason for that is their enhanced abilities when it comes to multitasking...and the fact that there is just more to an Intel processor.
Even though the P4 Prescott has a 31-stage instruction pipeline, it can still break off an unnecessary operation, or one running corrupted data, and start in on the proper thread with hardly a hiccup.
This happens with both but often is less obvious with a fast P4 as the Pentiums usually recover from common data errors such as branch prediction in less time than even an FX60 chip can.
And it seems that the older Northwoods were even more immune to this with their 20-stage pipeline, but even the Prescotts give up little. And they regain much ground when video editing or DVD encoding is the order of the day.
That's why I wind up selling so many CPU's for Intel; if AMD procs could boast similar durability and flexibility in the same price range, I'd choose them instead. There is no fanb0ism involved here.
And as for your new rig, buy a new PSU first. 300 watts just isn't enough, even if it IS an Antec model. My 3GHz Prescott rig gets its juice from a 480w TruePower, and I feel that is an excellent match for such a rig.
For a rig based on a PCIe MOBO, for goodness sake get a 550w or a 600w power supply, and make sure it is an Antec (or PC Power & Cooling, or some other top brand).
Don't skimp, even if it takes longer to put it all together...you will be glad later if you do it right now.