Alternative to phresh carbon filter?

I want a really effective carbon filter. I have a wind tunnel 6 fan I think it's just under 500 cfm, but I use speed controller to adjust temps. I'm currently at 30% power without a filter.

So I need to keep the flow rates high enough to not need to crank up that fan (it's a bit noisy)

I also need good carbon.

The phresh 6x24 550cfm seems to be a good choice, but it's so expensive.

Does anybody know a cheaper alternative that will perform as well?

Please note I do not have much room for really long filters. I could go a little longer but not much.

thanks for any help. I run 2 cool tubes off that fan, so if the filter backs it up my temps will spike and my fan will sound like a tank rolling through my bedroom.

I already wear ear plugs to bed.

 

p.s. I also don't want to build one. I have some design ideas, but i'd prefer the safety of a retail product.

 

bump?

 

at first I thought those wouldn't work, but I just looked at my fan box again and I guess I have 409 cfm, so they could. They are a lot cheaper in quality of build. I'm going to have temperature issues once a filter in installed so I'm looking for one with great flow. (i.e. oversized) Is the phesh really going to be as good as they claim it is?