The Fluval '05' series (105, 205, 305, 405) is not, in my opinion, worthwhile, but the Fluval FX5 is...and excellent filter, albeit a bit large for the needs of most tanks (the only change I would make would be the type of hose it uses, but that is easy to swap-out for about $15). With luck, Hagen will make the next Fluval series scaled-down versions of the FX5.
Eheims are excellent filters, and I especially like the 'classic' canister series, but Eheims are not inexpensive, typically running $200-$750.
A less expensive choice, that works quite well, and is easy to start/maintain, is the PennPlax Cascade canister series, although the 500 and 700 models are not really worth bothering with...the 1200 and 1500 models are very nice, although the media baskets could be a bit bigger and easier to manipulate.
I am not particularly fond of the Rena Filstars at all...I find that they have a habit of leaking and do not force water flow through the media the way that they should.