I own a Sirius. It's a good sounding and good looking platform for the modified RB250 that it's packaged with. It was closed out by the distributor and sold with arm for $1500 (new) which made it a good fit (price, performance and looks wise) for the modest system in my family room. I listened to both the P5 and Scout during the shopping process, but not in the same store/system. Honestly, how do you a/b turntables at different stores - too many variables.
I did get to a/b the P5 vs the Scout in the same system. I marginally preferred the Scout, but I definitely like the Rega arm better. I've owned an older VPI arm that was (inappropriately) mounted on my Oracle, with predictably mixed results. I also had some reservation about the VPI arm's mechanics and ergonomics and I've been less enthusiastic about VPI arms since that time.
In use for about 4 months now- paired first with a Clearaudio Arum Beta and then with an Ortofon Vigor HOMC cartridge, it has worked very well. Pitch stability ( a problem that has been reported on some other Transrotor tables) has been solid. I did cary the unit up to my main system for a brief a/b/c with my Oracle/Graham/Graham table and my Acoustic Solid/unmodded RB300/Ortofon Vigor ($2100 including cartridge). FWIW, the tables sounded out precisely according to price:
The Oracle/Graham/Graham was superior in every way to the budget guys, except that the Acoustic Solid provided bass that seemed roughly as extended, although a bit less tight. (The Transrotor set-up seemed to roll off a bit higher). This led me to swap the Ortofon and Clearaudio cartridges -to the benefit of both budget tables. The Transrotor still sounds tighter in the bass and the A-Solid more extended, but the gap has closed. The difference is now audible, but subtle. (I'm going to try an aftermarket weight on the A-Solid's RB-300 to see if that tightens up the bottom end any.)
In conclusion, the Sirius seems like a good deal at $1500 new plus the cost of cartridge. At $2100, the A-Solid represents a big jump up (although not in every respect- but I certainly prefer it overall). I believe that the Sirius is a good, competitive product at its price point but that the A-Solid represents great potential and a way, way out of market value.
Hope this is helpful.
Marty