You need a variable speed blower for the high SEER Rheem units. The RGTA is a standard furnace. Trane should be considerably higher if comparing an XV90 to these basic Rheems.
Now if you put the RGGD 13 stage Modulator against the 2 stage Trane, the Rheem will blow the choo choo away in COMFORT!!!!! plus give the performance & SEER the outside units are capable of. Also the 18 SEER 2 stage units really need a variable speed blower for best performance.