Honestly I wouldn't have a clue my friend. As far as I can tell you have a great system as is. I haven't spent enough time with the Pass amplifiers or any time with the VR4 to make a judgement. Since VS doesn't publish response graphs it's tough to know how the Pateks will fair.No doubt the Pass amplifier is a brute designed to drive a tough load when called to do so.
Two very different designed amplifiers for two different types of speakers.
Something tells me you're considering or will end up with a more efficient speaker in the future.;-) The Patek is a very low parts count design which could have its advantages when used with the right speakers. Same would go for the Pass on traditional designed speakers with crossovers that have lower impedances and crazy electrical phase angles.
If you plan to go crossover-less, then the Patek or some other low parts,medium to low wattage design like the Pass FW3 would be my choice. In the end, I think what ever speakers you decide to use will make the decision for you.
For low volume listening the HE crossover-less speakers will be hard to beat.
The Patek sounds like what ever you put infront of it. It will cover up nothing. The smallest change can be heard. So tube preamps are a lot fun as you can swap the tubes and hear the differences immediately without any guessing... even with a preamp that you aren't familiar with. It is extremely fast and transparent..there is no blurring of strings..etc.
For example, I had a very good internet audiophile buddy to mail me a demo cd from Sass microphones. This demo cd has all types of sounds from crashing waves to jet planes taking off to live acoustic music with drums..etc. There's one track where there's a person playing a drum kit...pretty hard at that.During the track I kept hearing a rattling as I played this over and over. At first I thought something was loose on the speaker. After further investigation I determined I was hearing the rattling of the metal ring around the base of the drum where you tighten down the skin with the wing type nuts. I was shocked that ...Not only could I hear the skin rattle on the drum set but I could hear the rattling of the entire drum. I've never heard this before except when watching a good friend play his drums 3 feet from me.Like I said the amplifier covers up nothing!LOL
Good listening