direwolfvt, the various Mesa Subway amps share similarities, but the differences between the TT, and WD models suit different types of music. I bought a D800 new, and a WD800 used. I would now prefer to replace the D800 with a D800+ because of the added features. I chose the WD over the TT because of the sound I want out of an amplifier. You can't go wrong with any of these amplifiers. If you do decide to buy one, I suggest that you also plan to buy a Subway speaker cabinet to go with it. Your use case will help you choose which Subway speaker is most suitable.
The bottom line is, there are no bad Subway amps, and speakers, and they all share a lot of things, but certain amps, and speakers are likely better for different situations, and types of music.
Tell us what type of music you play, and what gigging situations you will be doing, and you may get advice here from people who have similar needs.