I don't know if you read my big comparison of the Benchmark to a number of high-end soundcards, but it kicks them all in the nuts easily, even over the HDSP modded. I have not heard a Lynx card, so I don't know about their sound, but I really doubt it will beat the Benchmark. The benefit of the Benchmark is that you can use a cheapie soundcard like the Chaintech AV710 with no loss of sound quality, whereas other DACs tend to be more transport dependant, though that can be partially remedied by a device like the Monarchy DIP, but that adds the cost of the unit itself, another digital cable, another power cable...
I'd recommend:
AV710 -> optical cable of your choice -> Benchmark DAC1 (what I have
)
or
EMU 1212M or 0404M -> optical cable of your choice -> Monarchy DIP (optional, but preferred for best SQ) -> coaxial digital cable of your chioce (ditto) -> Scott Nixon TubeDAC (or varieties thereof) or Ack! Dack
Note I haven't used the latter potential system, it is constructed based off of the high marks trusted members have given those devices (save the EMU which I know inside&out).
Notice I haven't mentioned anything about staying with an internal card only. This is because you are talking about a price point that enables you to get more than any computer-only device I've ever used has provided, in terms of sound quality. The main advantages of staying with a card-only are low cost (not an issue for you), keeping it discreet (again, not an issue), or keeping it simple for simplicity's sake (ditto).