Only some observations here.
I think (I think) the Cavalier is not too dissimilar from the WaveMaster in size and other features. I could check, but it's a CM mid-tower. I dumped my WaveMaster because it was too much trouble (then) to drill the pop-rivets of the lower drive cage, cut out the front panel (behind the "monolith" aluminum bar), and install a 92 or 120mm fan. Also, I think CM's fans sorta suck, but . . . that's just me. . . .
Assuming you want to go forward with the case -- and it may not only be a very nice case but modifiable to a very "cool" case -- there are some questions. That is, I agree with the thought that your desk may be trapping heat, but some questions anyway.
How do you cool your X800 XL vid card? Is it the stock cooler?
Is the system OC'd with the Kingston modules? Do the Kingstons have heat-spreaders? Have you thermally sensored the memory to see how hot it gets?
Do you prefer room temps in the 80s of Fahrenheit?
How is the "regular CoolerMaster" CPU heatsink rated as to thermal resistance or (degrees) C/W (att)?
How are you exhausting air from the case?
The circuit traces conduct heat between components. I've found that cooling down the graphics card cools down the CPU temp reading, keeping the chipset cool does the same thing, and cool memory also helps.
Ultimately, though, looking at the Cavalier's design in the NewEgg snapshots, the front intake -- with or without fans -- is a paradox: it sucks because it doesn't suck enough. Definitely moddable, however, and you may have done it already.
You might try ducting the mobo and CPU-fan-exhaust out the rear 120mm exhaust fan. The case definitely has some potential there, too.
But for an AMD system, this tricked-out beauty of yours has a ways to go . . . even with the desk obstruction. I'd say look closer at these other things before you take a jig-saw to your desk.