Thanks for the reply linuxrulesusa, now you've got me thinkin. Should I buy a bigger pump and do like you, running sponges and back filters in some of my other tanks. I have my fry tanks in an adjoining room but could easily run air line through the wall to a few other tanks in my finished fish room and ellimenate(sp) some of the HOB filters. The finished room has 4-75's, 3-125's, 2-50's and 2-40's in it. I bought a watt meter and the HOB's run 7-10 watts each, so there may not be very much savings. I have 3 filters on the 125's , 2 on the 75's and 1 on the 40's and 50's. The next question does the largest sponge compare to a 300 gph a/c or emperor in either biological,mechanical filtration or both? I know most people run cannisters it seems but I have had no trouble water quality wise with 8-10x gph HOB filters and don't want that to change. Sorry to go on and on about this but I have bought to much equipment in the past only to replace it later.
I only do the HOBs so I don't have to vac fish poop out of the tank every other day. I could get by with the sponges. Sponges = bio mostly. Some waste as well but nothing like a HOB or canister. Depending on how powerful the air pump is, really.
The advantage of a canister is just space. You have more room for more media = more absorption of waste and more pores for good bacteria to grow. Downside is cleaning them, which I've heard can be a huge pain - never used them myself.
A sponge is better than a HOB at bio (except maybe an Aquaclear) for the same reason as a canister - more space for good bacteria to grow. If you want just a HOB, I'd upgrade to an AquaClear 70 or 110 (though 110 has almost double the space to put media in). If you want a cheaper route, add sponges - say $15 each if you buy new or even cheaper if you buy online, in bulk, or used sponges like at an auction. I've gotten Hydro IVs/Vs for $3-5 each sometimes.
I would skip the HOBs on fry tanks so you don't have to worry about them getting sucked up as well as since you'll be doing water changes more regularly on those anyway, so you can vac up the waste then.
HOBs definitely use more power - I can run two tanks with Hydro IVs off a 4w air pump (all mine are scattered around the basement so a closed air loop and/or linear piston pump doesn't work for my case). Compared to that, a 14W AquaClear 110 looks downright wasteful. Even so, heaters are what kill you on electricity costs. Heaters are probably 2/3 - 3/4 of your electrical usage for running the tank.