They are all very similar but have some definate differences.
1) JL Cleansweep - This is what I have running in my car and its excellent for what I need. It has a remote volume knob, so you cannot use your factory headunit volume knob (you can but it defeats the purpose). It will give an entirely flat eq signal. So you will need an external equalizer, use your computer to equalize, amps, or what have you. It is a very basic, but very good solution. JL Audio is awesome. But I'm sure you know that. Only has 2 pre-outs though, front and rear. You will need to have your amps do all the HPF and LPF.
2) The Alpine PXE - I'm not a pro on this one or the rockford, but I've got some research on these through my legacygt forum. The alpine is a good option and I think this one allows you to use your headunit volume knob, but I think this one also lacks an equalizer. If I remember correctly.
3) The RF 360.2 - From what I've read this is the most popular one because it has an equalizer and produces better bass response. Again, not 100%, but thats just what I remember about it. It uses a remote volume knob so you wont use your headunit volume knob. I believe this one also has 3 pre-outs for your setup (front, rear, and sub).
They all have disadvantages and advantages, but for the most part they are all very similar in that they take your factory headunit signal, convert it to a better signal, have outputs for your amps, have at least 1 input for your iPod, carputer, what have you...
Hope this helps.
~If your not living on the edge, your taking up too much space~
basically the 360 and the cleensweep are meant to be devices you install in an OEM vehicle to improve and control music clarity. The PXE gives you full control of each band including octave and cutoff points so you can fine tune the music for an aftermarket system. If you're looking to do tuning forget the cleansweep, the 360.2 would be ur entry level which allows you moderate control, and the PXE can be overwhelming with the number of tuning options it has
The 360.2 can be ran by bluetooth and can individually tune each speaker. but i maybe bias due to the fact i am not very familiar with the PXE. the PXE advertises as a factory integration along with the JL and 360.2 the only thing i have a question about the menu of the PXE does it only interface with the radio or how would you see what you are tuning?