...which in my opinion is pretty much half of the guitarists out there...
I think your market is much MUCH smaller than you think and I strongly disagree. What about:
* Bedroom only noodlers
* Modelling fans
* Mesa Boogie super gain metallers
* Stoner/Doomers
* People who only buy established brand names
* People who can't afford £850 for an amp head
* People who are happy with their current high end gear
* etc
* etc
None of the above would be interested in your amp :(
I'm not trying to be a douche-bag by the way, I just think it'll be tough to sell a very niche product in a flat market. As I said earlier, I wish you very best of luck as I don't think it'll be easy for you. It's the PR stuff that'll make the biggest difference to your success, not the product alone....