There's a free mathematical model for checking and comparing reflow oven capabilities at:
< http://www.ecd.com/products/profileplanner/ >
You don't need an ECD MOLE profiler to use this, its bascially an excel macro and pretty useful I found. It has some pre-canned ovens ad solder paste characteristics included, but you can tweak these to suit if you can't find a match or indeed create your own input to the model.
Might be useful to see what you have now and to justify something better
Nigel Burtt
www.enjaybee.com