It isn't clear from your post why you want or need the Hasselblad. The later Pentax 67 SMC lenses are excellent, and if you compare results to Zeiss glass (especially if you ever crop 6x6 to say 6x4,5 as many do) you will be surprised. Research the Photo.net archives, you should find test results. So I wouldn't switch systems just for image quality (unless you go for the most expensive FE range of lenses).
All that has been said above about the Hasselblad system and quality etc is true, and as you liked your TLR results, the 6x6 format should appeal. I have both systems, and use them equally. Some days I like the ease of handling of the P67II with its excellent meter; other days I like the considered approach demanded by the 'blad (it can fool you in many ways!). Always on the tripod with the 'blad, not always with the P67 (with Tri-X or HP5 plus). They say a 503CW with winder and prism make a better handheld camera, but havn't tried that yet.
With used prices so low, you could get yourself a second P67 body as back up and for a different film type.
Why do I keep both systems. Firstly, prices are cheap, expecially the P67 stuff. Secondly, much as I admire the square view in many circumstances, I am always drawn to the big 6x7 negative size. The Plaubel Makinon 67 suggestion was good, with eye-level viewing, although not everyone would like the rangefinder viewer.