If you have the credits buy them. The old Burner 2 were good, perhaps even great, irons in their day but sadly their days are over if you want to play as well as you can.
You really won't regret upgrading. It always used to be said that the 3 and 4 irons were killers in each new club set and while that's true of the Vapors you also get a brilliant PW. It's damn near as good as the top of the range wedges we pay silly amounts for in the pro shop.
Do it.
Quickly.
Before someone at WGT realises they shouldn't be in the shop any more.