I'd agree with that. Why would you buy an amp before you even know which speakers you're choosing? Even if it has sufficient power, how do you know its native sonic character is a good match for your tastes much less if it will match well with the speakers you eventually choose?
Also, you mentioned 2-channel music is important to you. If that's the case you'll definitely want to bypass the receiver's preamp section along with the amp section. An elegant and cost-effective solution to this would be an integrated amp with a HT bypass input. With the Hafler you'll still need to buy a stereo preamp, which is no big deal but it adds another box (and another pair of interconnects) to your system.
I dont mean mean to be preachy here, but I'm just saying that taking some time and thinking things through rather than making impulse purchases can (and will likely) save you time and money and get you better results in the long run.