What the benifit of using a separate dac?

Jax2 - It depends when you listened to Benchmark. Early ones had Signetics/Philips NE5532 Op-amps that sounded thin. Around 2001/2002 Philips had factory fire (burned down) and stopped making them. Texas Instruments bought the license and designed new larger die that sounds better. Benchmark also needs a little time to get civilized but even after hundred hours doesn't sound warm (if that's what you're after).

Kijanki - I listened at length to two versions. One was an early version, but post-2002, which was thoroughly burned in. I listened in three very different systems to that one. The second was more recent and was a current, USB version which I ordered direct from Benchmark. Again, I listened in two different systems to that one. Since this was from the factory I had to burn it in myself. By the time I returned it I'd estimate I'd put around 200 hours or more on it by leaving it on whenever I could, so I don't know if it could have sounded better given more time. I don't know whether it came from the factory with any hours on it since they do have the return policy. The latter version was definitely an improvement over the former, but still suffered from stridency in the high end which ultimately made it difficult to listen to for long periods. I found it on the colder side, a sound I'd associate in some ways with SS amplification. OTOH, I heard it in several systems at RMAF and I very much like what I heard there, but I did not listen to any one at great length to determine whether any similar traits to what I heard at home existed in the long run. I have no doubts it can sound good to some folks - clearly it is praised by many - it just did not sound good to me, rather, in my systems in sounded clinical and a bit harsh. In comparison I much preferred an MHDT Paradisea which presented the same music with a much more natural presence. The early version I had I compared to a Wavelength Brick and a very old Muse Model 2+ both of which I preferred, the Muse being more similar to the Benchmark, but not nearly as harsh, while the Wavelength was a sharper contrast being a kinder gentler presentation. I believe all the DAC's I preferred were NOS DAC's if I'm not mistaken. I also tend to like DAC's and players with a tube output stage in general, though not as a rule. As with everything here, YMMV - to each their own.

Thanks so far for comments, its hard when it comes to digital, I live a long way from major cities, so trying in home is impossible, I buy all my gear from all over the world as lot of the brands are not available and plus work commitments have there restraints on my time, so far I bought everything I have using reviews and chat on Audiogon and have been very happy so far.One last question if a Wadia player is so good why do they have to be moded?

One last question if a Wadia player is so good why do they have to be moded?
K_rose

Its not that Wadia product HAS to be a mod candidate,but what the audiophile desires, in his or her particular set-up.
Wadia, like any company, has price constraints when a design goes to market. If the moding company(GNSC comes to mind) can make a Wadia sound all the better, then IMHO it is money well spent. Think Synergy...

One last question if a Wadia player is so good why do they have to be moded?

As an addendum to the answer above - Modders tend to choose some of the best platforms to build upon because it has the potential to show off their work on it even more than a modest component might since the construction that is already there is very stable and revealing to begin with. In a similar way you may experience this if you start investing effectively in better and better components you tend to find that your system becomes more and more revealing of any changes you make to it (at least that has been my experience). That's also the ticket to the merry-go-round, or the sure sign of a bad case of Audiophilial Nervosa. Also, in some cases, components are considered for the space available within their chassis to build into (an Oppo player does not have much room to add anything, though there are mods for them), but I'd guess that would take a back seat to the consideration of what is there already in stock form. There is probably also a psychological component as well - Folks who are willing to invest serious $ in modifying a component for better performance may prefer to be investing in a solid platform that has bling factor, pride of ownership and all that. Are you going to want to spend $1200 modifying a $170 Oppo player? None of this suggests you have to choose this direction. My experience with modded products (GNSC, Modwright, APL) suggests very strongly that skilled modders absolutely can make a significant improvement to a component. I'm sure there are also those out there who do mods who are taking advantage of this, but are not necessarily as skilled as others, who do not make a big difference. If you are considering a modded product I'd do some real-world research on what folks have to say about their experiences with those you are considering. You also may want to consider what mods do to the resale value of the product. In the case of the modders I mentioned they certainly seem to hold their value in most cases.