Have to agree with the last two posts about the Fluvals. I just got a 304 for my 55 gal about a month ago. It runs great (though there is a little rattling, I think I may need to take the top off and re-seat it), fairly quiet other than the rattlign which I think is user error, has great filter media accessibility.
Just a little note about all this priming talk: It is a complete non-issue. For me it is at least. The 304 and anything after that has this feature called "aquastop" where with the flip of a valve, you can completely stop the flow and keep the siphon, and then remove the filter from the hosing in about 5 seconds. So long as you fill the cannister back up with water (preferably tank but you can use tap at the risk of losing some ben bact filtration) you can just hook it back up to the hoses, open the aquastop, and plug it in: no priming needed at all. The one and only time you should ever need to prime it is when you set it up for the first time. You may have a much harder time priming it if there is a leak or something, or the hoses aren't underwater when you're trying to do it.
I think they're all great and love canister filters. I only have exp. w/ a fluval but can tell you that I LOVE my 304 for $55.