Bernie,
in my opinion (amateur at home playing for myself), Hypercanvas provides a very quick and acceptable solution to GM/GS/midi file player/simple accompaniment needs. Driven by my own keyboard's styles, the sounds it provides have "freshened" my sound palette.

Its sound quality is inferior to more modern approaches, (on the other hand it has a more "dirty" sound and that may be of benefit sometimes) but I find that it is very quick to understand and tweak, and the interface is (again IMHO) flawless.

Along the same lines, HQ Orchestral is a very good solution foe orchestral pieces with very good orchestra instruments and Superquartet casrries a good selection of everyday Piano, Guitar, Bass and Drums voices (some with velocity-triggered affects such as slides etc) with better quality than Hypercanvas provides.

Drum and Bass Rig has a fair selection of basses and drum sets, quality easily surpassing everything Hypercanvas has to offer, but they are WAY more demanding on the CPU.
(Two instances of hypercanvas play at 15-20% on my CPU, add Drum & Bass rig and skyrocket to 60%, just substituting the bassline and the drum channel.)

Key Rig has a selection of piano sounds, (adequate IMHO), a simple? (never tried to operate it) synth, a Hammond module and a GM module which sounds crisper than Hypercanvas but IMHO lacks the "integrity" of the Hypercanvas. (Hypercanvas sounds tend to complement each other in a mix, they seem like a "collection" of sounds rather than a "bunch" of sounds thrown together. But it is good.

Bandstand is supposedly superb, carries very big samples but...... it doesn't sound like it to me, either by headphones or with speakers. (Others here share the same opinion).
Also, it responds to GM program changes, but it takes A LOT of time to change. A simple change of style in my setup, takes maybe 20 seconds to completely change all the instruments in bandstand, and since you probably will play it live, it won't do, I think. Faster (more dedicated) setups will give you faster responses but not "point and click" fast. Some loading will be required.

Luxonic Ravity is a synth module with very good capabilities which exceed my knowledge of synths by 95%. It has a good selection of basses and synth leads and other synth sounds that sound very good to me, but is probably geared towards modern music (house, techno etc).

The B4 Hammond demo I have heard and played sounds very good, but for me to even attempt criticizing that sound would be immoral, since I havent even seen a live B3, let alone play one. Others here know better of the real thing and the softsynth also.

Of the others, Kontakt and the more expensive sound libraries like Garritan and such, I know nothing.
Hope it helps somehow.
Please share with us what you find about the Receptor.
Theodore

PS if you manage to take advantage of the style buttons, variation buttons etc on your arranger it will be a godsend. you just continue playing in a platform you know and take advantage of the better sounds where available.