I mostly wear a pair of Mendellson own-brand HM40s which are an excellent price and as good as David Clarke's in my opinion, without the high clamping forces. They work well for the environment in which I do most of my flying, and have very good passive noise attenuation. I would have no hesitation in recommending them.
However, it's absolutely true that you can concentrate on learning much better with a lightweight ANR headset like the Bose. I used a borrowed one for my CPL and it made a very noticeable difference when I made the switch. If you are definitely going all the way with your training, then the investment now is a pretty good idea. You'll never prove that, but the odds are that it'll pay for itself in the reduced flying hours to get your licences.
G