I waas wondering what the HP and top end and low end etc. differnce between these snowmachines are?

Regular MXZ 670 = 118hp

MXZ 670 HO = 125-130hp

MXZ 700 = 122-126hp

If you're looking at buying one of these 3 machines, I would suggest the 670HO. Good motor, good suspension, lightweight, reliable.

My $.02 is: the 2 sleds will speed wise be very close. 1 will say the 670 is faster and the next will say the 700 is faster. The big improvement is in the chassis. Personally i think the 670 will hook up off the line better which is nice for grass drags. On the trail i would hands down go with the ZX chassis 700. Both sleds can be built to haul the mail equally but you can do it easier on the 700. I'm sure some will say their 670Ho is the way to go, yes they are fast but the ride doesn't compare to the ZX. I guess it comes down to price and your riding style.
When i bought my 2001 MXZ 700 i was looking for a 670HO and my uncle talked me out of it and i got the 700 i can't thank him more. just my $.02

i've had both the s-2000 and zx chassis, and there is no comparison. the zx chassis(sc-10III and precision ski's)is far better in every way possible. stability, cornering and ride are awesome.