If you can afford that, I would go for a Roland TD50x with Superior Drummer or similar VST library then you get the best of both worlds and will never look back, if you don't want the Roland look you can get a Drum-Tec kit with the Roland Module (and the included samples which allow you to use only the module and are very gig ready).
Drum-Tec sells other expansions but you can create those yourself too. Just learn how to import and blend samples into the module.
The differences between the Roland module and the Alesis module are that you get much more customization with the Roland but you get the touch screen with the Alesis... sounds are subjective,
I believe, no, I know you can get good usable sounds with the Roland modules if you spend the time dialing them in, same goes for Alesis which I have owned the DM5 which surprisingly has aged well.
Other differences are Roland's proven reliability (I have had a TD-11 kit for over 12 years and not a single part has failed me). Prior Alesis kits had lots of reliability issues with pads failing all the time (you certainly don't want that on a supposedly flagship kit). Granted Alesis seems to have corrected those issues, their reputation still suffers.
Another route you can go if you don't want to spend that much is buy the module with the digital pads (which drum tech also sells), buy the triggers and cymbals and convert any acoustic of your liking into your custom kit. Even doing that, you will probably still end up spending less and get exactly what you want. Jobeky also sells cymbals and drums you can use to create your kit.
Custom Electronic Drums, Shell Packs, Electronic Cymbals, Electronic Trigger Bars, Full Electronic Drum Kits, Modules, Mesh Heads And Accessories.
jobekydrums.co.uk
That is the way I would go if I was building a kit from the ground up and had that budget.
you could end up with something like this:
(not sampled kit though - synthetic models). Oh, and chuck a DTX into your shortlist. Alesis has bugs at the mo - and the pads can be a bit fragile - Yamaha or Roland for known build quality (Yamaha is multilayered samples + individual cabling, Roland is models and cable snake on most models)
