School me on the best machine for big hardwood

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Your requirements are not a million miles away from what I want to end up with, except mine will be used for building high-end loudspeakers rather than guitars (hence needs to be a bit larger); I've also had to think about the relocation issue. My advice if you're going to build your own is to go for a "raised side rail" arrangement, as then it's pretty easy to make the gantry detachable which would obviously help with moving the thing. But even so, I wouldn't be expecting the base part of anything that's properly rigid to be a one man lift - however if you're making one yourself you can of course build in handles/lifting points and provision for mounting it on a dolly or similar. I've also had a word with my pal Mike Vanden, one of the best archtop luthiers in the country, and he said don't get too hung up on feed rates as with some fancy hardwoods you can get a poor cut if you go too fast - he tends to work his Isel machine at 2000mm/min tops on standard wood and less if doing fine work on brittle stuff. A lot of the problem is that wood isn't a completely even material and some hardwoods are a bit on the brittle side; if you hit a hard spot/twisty bit near a corner on the end grain you can easily take a wee chip out of the edge. Using downward spiral cutters and machining the end grain first can help obviously, but won't solve everything all the time.
Regarding your comments on the K2CNC machine, it's difficult to say exactly what size that spindle is, but assuming the square rails are 20mm, I guess it could be a 2.2KW aircooled thing. Although servos have better torque at high rpm than steppers that doesn't mean you can't make a machine that goes fast enough for your kind of work using steppers, it's just a matter of getting the design right, there's a very useful motor/ballscrew calculator on this forum. And then there's now the closed-loop steppers available which are kind of a half-way house.