Is it possible to switch to YASM?

[stan_wkc]

AFAIK, NASM does not generate 64-bit code on Linux x86-64 target.
This makes some nasm-compiled object files could not link with
the encoder. mppenc's speed falls from ~20x to ~16x
on my Athlon 64 3000+(S939) with profile "standard".

From what I have heard, YASM, a replacement of NASM, could generate 64-bit code.
Currently it uses an extension of NASM syntax to support x86-64 assembly.
IMO those SSE registers do not change much. With a little modification,
is it possible to go with YASM?