I have a pair of SGR CX4 active speakers that are quite similar to your Paradigms. I recently got an ITube2 and tried it out in my rig as a buffer and a preamp. But to relate my findings and experience back to your question. Note i used the IPurifier 2 on the 15v IFI PSU into the ITube2 and both tests below.
Using the outputs of the Pana - ITube2 (in preamp mode - no gain setting, classic tube sound) - SGRs. This would give you the best bang for buck experience. Its 'reasonably' transparent as a preamp, but once you active the 3D, or Bass boost or SET/PushPull signature switches, it wont be and it does alter the sound. Note that, i used a 2m long interconnect from my Pana UB9000 player's rca outs to the Itube2, and another 3m pair out to my SGR actives. I managed to get reasonable output with these length cables at the volume control dial at 12 oclock position.
I also tried it with a simple Tisburry passive preamp (as a preamp) and ran the ITube2 as a buffer stage after. It looked like this: Pana RCA outs - Tisburry passive - ITube2 (in buffer mode, +6db bass & classic tube sound) - CX4s. added another 1.5m cable from the Tisburry to the ITube2. It sounded more transparent/cleaner than the former config, which i preferred. I augmented the bass with the +6db bass boost, which didnt smear the mids/highs at all IMO.
Insert a caveat here: I took the ITube out of the chain and ran it through my Modwright LS100. More bloom & colouration in the sound. So yes, the ITube as a preamp was more 'transparent' than my Modwright.