I'll clerify further. THe Rheem is $1000 more than the Keeprite and the Lennox wasn't much more than the Keeprite. My opinion is the same. Although I feel Rheem is better than Keeprite, it's NOT the Lennox G61 and how it's possibly that much more makes no sense. Rheem stuff to keep the comparison going averages $200-$400 less than the Lennox.
Also consider the Lennox (and the Keeprite for that matter), would qualify for the $1580 rebate assuming you're replacing a mid or older.
At the same time, you have to be comfortable with the contractor, as the install to your application is very important.