Well, a (very little) looking and you would find that the Tvix 5000 is by far the most capable and popular device, with the new 4000 also receiving much intrest.
My god man, look at the other threads and it is in right in front of you! Sorry-No offense.
So, I have the Mediagate MG35 (collects dust) as well as (2) Tvix 5000's (bedroom and office HDTV's-45") and will soon order a 4000 for my living room HDTV. The tvix boxes flawlessly play both SD DVD's (either file mode or ISO rips) with full interactivity, as well as 1080 HD transport streams without narry a stutter, pause, dropped frame, freeze, or pixellation over a WIRED ethernet connection from a PC or NAS (Infrant ReadyNAS NV's).
Since the 4000 just hit the shores here, and there are a couple bugs it seems, I am waiting a few weeks for these to be resolved before I order a 4000. Kinda like a new model car-you never want one of the first batch of the model since they are still debugging the product.
The Mediagate, DLink, Buffalo, IoData, Linksys, Helios, and others are either severly crippled, buggy, or worse-just dont to what they advertise! Buyer beware. I have been had 4 of the above at one time or another and have been burned and wasted good money on their products. Never again will I buy a product from these guys.
But it depends on what you need/expect. From your comments it seems the Tvix will do what you need splendidly, especially HD mpeg2 ts's over the network.