Lyngdorf 3400 headphone amp quality?

If you’re at all serious about headphones, get a dedicated headphone amp.  Headphone amps in integrated amps are, with very few exceptions, afterthoughts at best.  Amps matter as much with headphones as they do in home systems, so while you probably can get by driving your ‘phones from your integrated, are you looking to just get by or for better sound?  There are lots of very good headphone amps out there these days that offer excellent performance without a huge cost outlay.  A good example is the Singxer SA-1 that I own and for $599 (can be found under $500 used) is a fully-balanced, Class-A amp that offers plenty of power and sounds very open, neutral, and natural driving my Hifiman Arya Stealths.  Anyway, just my $0.02 FWIW.  

Thanks for your thoughts.

Anyone have experience withe 3400?