I'm using Zalman CNPS6000-CU currently with my 1ghz FC-PGA2 CPU. It should have more heat dissipation than yours.
just as comparison, CNPS6000-CU has 2600-2900cm^2 of surface area.
I can't find the surface area of Slk-800, maybe you can figure it out for us.
and I'm using Zalman's 92mm fan rotating at 1600rpm (I can't find the CFM spec of this fan at this rpm range, but this should give you a very rough idea where you should be). That cools my 1ghz P3 CPU down to about 30-40*C idle, and 48-51*C (loaded).
Zalman solution may work. I've cancelled my SLK-800 order, so I can't tell you how that may work with other thermo fans. But I think you can get away with SLk-800 with panaflo L1A @ 5v. of course I won't be responsible for my suggestions