The XCAN v3 will most likely sound excellant with the K701 (others have reported it does), since it does so with the HD6XX's, and all Grados - assuming you have the right set up to complement them. It would sound especially good with the PinkFloyd mods. And of course it's a major value, comparing favorably to much more expensive amps.
However, from what I've read in the various reviews of the K701's is that they may benefit from a tube amp with more tube-like SQ, since they're so neutral by themselves. As those above have noted, the XCAN v3 is a tube hybrid, and has more of a SS SQ than SET tube SQ. Although, drarthurwells swears that they sound great with the BADA PH12 (also a tube hybrid).
I guess, if it were my money, I'd be tempted to try the BADA PH12 (you can get if from Pacific Valve with a 30 day satisfaction guarantee), or the Woo Audio 3 (only with the upgraded tubes - it reportedly sounds as good as the SP's and Raptor for half the price), or, if you don't mind spending a lot more - the SP PPX3 Slam with the upgrades.
But... if you don't want to spend more than $300 to $400, you will find it difficult to beat the XCAN v3.
GF2