...I'm of the mind right now that starting with Real Tubes is the way I have to go. Seems, indeed, there is nothing like real tube tone and digital can't really capture it. Must be a spiritual reality there somewhere. Fire? Agni? The 3rd evolute of Brahman? I don't know...
I used the Real Tube effects, pedals and rack-mount, for several years, and very much enjoyed them.
Since then, I have switched to Digitech pre-amps and processors. They don't sound exactly like those vacuum tube even-order harmonics, but the programmers at Digitech know how to get a pleasing guitar tone with lots of accessory control for the user to tweak the sound. More control, more versatility, and a very large selection of electronic effects. Very clean, quiet, and all in the same durable, compact enclosure.