I think the Whole internet is having problems. My other usual websites are messed up, too.
A TE60 has a Larger compressor, while maintaining a TE44 Turbine. Like above, I'd do that before going to a 51 (Same compressor as TE44, different turbine wheel)
If I where in the market for a used turbo, I'd pay $400 for a known good, low mile used TA49/TE44, but I don't think I would go that high for a 51. I'd want a warranty.