After many years with a Rivera Knucklehead valve head through a 4x12, I took the plunge, and bought an Axe fx and Matrix GT800fx. Unlike most of the guys on the forum, I run mine in stereo, with the cab being wired for 2x8 ohms. I find the chorus's and delays to be fuller this way, and dont find any of the phasing issues that others have reported.
Now, after some six months of editing and tweeking, I dont miss the Rivera at all except for the weight! Besides doing the usual turn the sag up, I found that turning the patch master volume up, and patch level down, made for a more compressed sort of feel, and like many others on here, I dont find the 'playing feel' now any different to a valve amp, with lots of sustain available, and with the Matrix being solid state, I dont have to worry about the valve amp 'sweet spot' when playing in small venues, as I always get a good sound at any level.
My 4x12 is a Marshall, with Celestion Vintage 30 speakers, though I also have a Rivera cab with the same speaker, which I use for editing at home, to ensure my stage settings are correct. As a matter of interest, I was able to carry out a good comparison between the Vintage 30, and the Celestion G12/75 and found that the Vintage 30 was a more focussed sound to the G12, and was able to cut through the mix more.
I find that the Matrix removes the need to play above a certain level to achieve the 'sweet spot', and after some 40 years playing through valve amps, I am a firm Matrix convert.
Im sure that with a bit of patience, you will get the sound that you are looking for.
Good luck