While I'm sure your instructor was trying to give you good info, unless you all have several hundred dollars you don't have a better use for, just use what you have in hand.
The headset use from pushback rule isn't going to change even if every new hire runs out and buys a Telex, and I strongly encourage you all not to do so just because your indoc instructor prefers them, unless of course, he's buying

.
A regular set of DC's or any other full coverage headset will provide more than enough sound attenuation, and my 13.4's have been perfectly compatible with both the aircraft comm box and every other headset I've talked to. It's really more important that they be comfortable through a four- day, 24-hour block trip.
At the very least, wait until you get on line and try out your existing headset for a while, that is unless you have money to burn.
By the way, for anyone who doesn't show up with a set of Jepp binders, you can get them from the folks in Tech Pubs in the GO building at a deep discount and payroll deductible to boot. I needed three 3 inch binders. Some folks also make up 1" trip binders so they don't have to pull out another big binder every other leg. Your choice.
Good luck.