Ray:
I just purchased a Eheim 2026 Pro II and a Magnum 350 Pro (with Bio-Wheel and Gravel Washer). I've read alot of good things about the Eheims and Magnums. They are actually on their way, so I don't have them yet. I got the Magnum for the polishing capability, gravel washer, and Bio-Wheel. I will hook the output of the Eheim to the Bio-Wheel to agitate the surface and provide good bio-filtering. I really like the Bio-wheels. Anyway, I've seen several fish stores running the Eheims. Also, I've seen them selling for over $100.00 more than what I paid for mine. To be honest with you, they aren't that much more than the Fluvals if you get'm at a good price...online. I have also heard some good things...and bad things about the Fluvals. I've heard that they are somewhat difficult to get a good seal...and that quality is sacrificed for price. Also, I've heard the Fluvals come with REALLY poor/confusing instructions for setup. Overall, I would recommend the Fluval if you are tight on cash, the Eheim if you have the little extra to spend...and the Magnum if you are looking for diversity and the water polishing capability.
Hope this helps,
Bombay