Hi Crazyforblues,I have no experience with the Aleph 30.But I have no doubt it would be a great match with either.It depends on what your looking for.The 6.3s would have a bit more weight and impact on the music.The sound is a little fuller with the 6.3s.And they are just as efficient as the 5.3s.I was just experimenting with a 15 watt triode amplifier(only 12 lbs) and the 6.3s.It had no problem pushing the 6.3s well above my normal listening levels.I really like the Sols with some good class A power.I suspect your setup shouldn't leave much to be desired thou!You would be moving from a 3 way to a 2.5 or 2 way design.
I was communicating with David Berman of Soliloquy just the other day.And he told me some details about the designs I hadn't been aware of.The 6.3s and 6.5s both use a staggered design.The drivers don't hand off from bottom to top.Which is the norm for a lot of designs.The bass driver is actually above the midrange driver in the 6.3s.The 6.5 inch drivers are also different,even thou they look the same from the outside.The magnet systems a larger in the 6.3s than the 6.5s because of the stress put on them to handle a wider range of freqs.These little drivers weigh 6 lbs a piece,I have some Deftecs for HT with 6.5 Vifa drivers in them,it takes two of them to equal the weight of one of the drivers in the 6.3s! Either way you go wouldn't be a bad move....since your a fan of the Soliloquy sound.And familiar with how to set them up properly.