Time for a Pre change? Need the wisdom...

I cannot remember if you told us what amplifier you are using.  I don't think the Parasound P6 preamp is going to be better than the McIntosh preamp.  It is definitely newer.  Oh yeah, you're using that Crown Class D amp.

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When looking at current generation amps, the McIntosh will actually have pretty good resolution on the high frequencies, but it will be laid back in the midrange for sure.  The Parasound will have softer and rolled off highs in some speakers, but it will have good attack and slam in the midrange.  The choice between these two becomes a factor of personal taste and synergy between components.

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As I said, my cousin has the Aerial 10T.  He has a very high resolution Krell preamp with silver XLR interconnect cabling.  Currently, he has Emotiva XPA-1 monoblocks, which we had to upgrade with Isoclean fuses to "take the edge off".  We also had to switch the speaker cables to solid-core Audioquest Type 8 with gold-plated spades.  This further helped that harshness.   As I have said, I am bringing down my Parasoiund JC1 amps (fully loaded with Furutech fuses) to see how they sound on the Aerial 10T's tomorrow.   I can send you my results.

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I think the harsh edge on your 10T is due to two things.  One is the metal dome tweeter, which has a breakup/distortion slightly above the 20khz point.  This causes enough of a problem where the high frequencies can sound harsh/bright.  The second problem is the kevlar midrange, which also has a cone flex/breakup characteristic which can cause harshness/distortion in the low high frequencies.  I would keep your McIntosh C41 preamp for now and experiment with solid-core speaker cable and a different amp.

@captbeaver - The 7T are COMPLETELY different speakers than the older 10T.  The 7T use soft-dome ring radiator tweeters and a paper cone midrange.  I would probably put the 7T as a "Sonus Faber" type of sound.  I think the 7T would really shine with a very high resolution amplifier, but of course it's all up to your taste.  There are a hundred different directions you could go.  It's difficult to say if the Parasound would mate well with the 7T or if it would be too warm (unless you like that slightly warm character).

I actually have used those 10awg Beldon speaker wire from Blue Jean.  It makes an okay subwoofer speaker cable, but they overall lacking in my opinion.  They lacked the high frequency resolution and made the system sound "low fidelity" in a sense.  Even the normal 12awg stranded OFC copper "Monster Cable" speaker wire were higher resolution than the Beldon.  The Beldon is a bundled copper - I don't think it's even OFC.  Just so that you know.  I guess if you want to roll off the highs, that's great, but it won't give you the "air" and "depth" that other speaker cables will.