Although I can't comment on HK's new line of receivers, I just replaced an HK receiver with the NAD T762 and am extremely pleased with the NAD. I don't think you could go wrong with either, but to my ears NAD has the edge in musicality and home theater applications.
Although I didn't get a chance to hear the 742, I did hear the 752 and found it a very competent receiver. NADs and HKs seem similar in the respect that both rate the watts per channel conservatively, but in presentation they sound very punchy and dynamic.
The NAD T742 has pre-outs for all channels (5.1) and that will come in handy if you have a very large room or need extra power for very high listening levels. I don't think you could go wrong with the HK or the NAD, but I would recommend NAD based on owning both. The sonic character of NAD (to my ears) is more neutral and musical and is a perfect match for my Axioms. Good luck in your reciever hunting,