I've had a fair number of higher end receivers (excuse the oxymoron), and in all cases found they performed better as preamps* than amps. Always found a not-subtle improvement when using an outboard dedicated amp (regardless of speaker character/efficiency, but certainly more pronounced with demanding loads), and varying degrees of more subtle improvement when using outboard preamp and HT passthru. The nice thing is that it provides a nice incremental upgrade path if you are so inclined.
*Excepting for the phono preamp if it happens to be built-in, which are universally pretty lousy.
*Excepting for the phono preamp if it happens to be built-in, which are universally pretty lousy.