VERY GOOD Deal!
I'd agree on keeping the 24-105mm F4L. Even the 40mm f2.8 is quite sharp. Let's say you sold ALL the lenses, using what I feel is conservative pricing:
$750 - 24-105mm
$300 - 70-300mm
$100 - 40mm
That puts the body around $1487, UNDER $1500!!!!
FF for $1500 is very tempting. I just invested in t3i, kit lens and sigma 30mm. May be it is true early to get rid of them and move to FF. I need to learn about raw shooting first.