DnJ90
I'm with cincyreefer on this - I would keep the wet/dry over the HOB power filters.
I'm a big fan of having an overflow and sump/wet/dry, so my opinion will always lean that way. Especially on larger tanks like yours.
It's certainly possible to use two of the Aquaclear 500's, if you prefer.
You say that the filter has always been your down fall. What kinds of problems did you have in the past ?
Setting up a tank utilizing a combination of some live rock, sandbed and possibly a planted refugium would be worth looking into in my opinion. Protein skimmers are another great option for many folks as well. You may be able to a very nice successful tank - without the need for the bioballs in the wet/dry, or the need for the two HOB filters.
A lot of people do set up there tanks this way. It all depends on what kind of tank you want now versus what you may want in the near future.
A wet/dry, with or without biomedia allows for some flexibility over the HOB - again in my opinion.