If you have an amp with a nice clean, the Zendrive will get you in the ballpark.
I built a ceriatone OTS FM50 for $774 minus tubes and head cab.
No pedal will ever get you the feel that the D-style amp has.
I went and got a zendrive because I saw RF use one with his Dumble #102 and thought it sounded great!
I barely use the Zendrive because with it engaged on the clean channell I get the same exact tone but better from my OD channel with no pedal!
So $200 for a little box that gets you in ballpark
OR $800 + some tubes and woodworking for an amp that does get Dumble tone.
My suggestion is to save up and get the real deal.
BTW I built a couple pedals before getting into amps and I actually find it easier to work on the amp because there is more distance between components. Just make sure you do your homework if you go this route, there is a lot to digest! Main thing is to do good solder work and learn how to work on it safely.
My 2 cents
Todd
Ceriatone OTS FM50 build #1,Ceriatone 2550 build #2, Ceriatone HRM w/ EL34's build #3,
Trainwreck Express clone build #4 More to come because I am addicted now!
Steve Morse signature EBMM original model ,50th anniv American Strat