You don't say which Techno but I'll assume it's an LC which is a much more capable machine than the K2 but they'll both seem like toys compared to your Haas. Lots of luthiers using both machines so depends on your budget and what you can put up with on cut speed and accuracy. Having a fast machine (>250ipm) for finish toolpaths would save a lot of time. Necks and fingerboards require a bunch of different bits/mills so manual tool changes are going to be a pain even if you use gang fixturing. You'll want to option up the K2 with ballscrews, slides, and servos. Get a spindle for either. Highly recommend upgrading Z-travel to 8" pref 11" in case you do more than bolt-on necks.
I have a Techno gantry with the stock 250ipm servos which isn't quite as capable as their LC's with its heavy steel base and better slides. ATC, big spindles, faster servos can be optioned out. Their PC based controller is very stable, runs on an inexpensive machine and only takes minutes to get running. It's very simple compared to your Haas.
It'll take a lot of necks to pay for a machine compared to Warmoth or you might want to talk to Bob at saintlutherie.com or John at cncguitarparts.com