Hello Toadster!!!
I have an Antec Sonata with a 3.4 gig CPU. I also have the original 120mm case fan in back, and I added an Antec 120MM smartfan behind the drives- pulling air in. However- I was using Stock POS Intel cooling.
My TEMPS were just like yours, and as soon as I did ANYTHING intensive- I was Throttling.
Comp-USA had a sale this week on the Zalman 9500 for $60. I bought it, and removed my old stocker, and cleaned the CPU real well, and added Arctic Silver 5 and put the Zalman on. I am now using only 1 fan(rear), and I am also running 4 7200 rpm drives in my case.
Zalman has been on since Thursday night, and my CPU temps have dropped from 57C idle to 42C idle. Running Prime95- I am only at 55C!!!
We are essentially running comparable hardware- except I have a little more to add heat, and my temps are 15C cooler than you. You MIGHT want to try removing the heatsink from bracket, and reclean getting rid of old paste and re-applying Arctic Silver. With what I just did, and the results- I am a believer!!!
Good Luck
Chris