So, today I got my A-400 (I'm in Germany).
I posted a longer review (or a bunch of first impressions) over here, but it's in german: http://www.hifi-forum.de/index.php?action=browseT&forum_id=181&thread=9102&postID=75#75
To summarize a few points in english though: I've been using a Oppo BD player and a Dune Smart unit. Both paired up with external video processors (also with VXP processors). The main reason why I got the A-400 was to check how good the Sigma 8911 is and if it can replace a Oppo + standalone VP for SD playback. In short: it can't.
The A-400 looks and feels nice and doesn't even get warm after 4 hours of use (without internal HDD), but the current firmware (the one released yesterday) is extremely buggy. I had of lots of crashes, either when starting or ending MKV playback and a few times on the info screen as well. But I guess those bugs will be fixed in the long run. Just wondering why the essentials can't be fixed with the Popcorn Hour players around for years now.
The HD rips I tried (MKV) all played fine, but I was really disappointed to see what remained of the VXP features. I mean, hello, the "big" VXP processors came out in 2006 and 2007. Gennum was purchased by Sigma in 2008 and 4 years later, Sigma can't even bring the full VXP feature set to it's flagship decoder/processor ? 3D Noise Reduction, Block Artefact Reduction, Mosquito Noise Reduction - all not available. What's there is the adaptive contrast control (which is silly since nobody likes it anyway and those who do can use the same feature on their TV set). I was looking forward to the deinterlacing features, but they're not great. In the menu VXP deinterlacing can be set to on or off and it switches the A400 from a simple video deinterlacing mode to the VXP video mode. I tried a bunch of DVD rips with hard telecines and the VXP was not able to switch into film mode - not even for a moment. So I don't see where the "adaptive film mode" ads come from.
The VXP's video deinterlacing is nice, not great though and NOWHERE as good as the deinterlacing on any standalone VXP processor is or was. For people who know other processors: I would rate it below the ABT2010/15 and below the Marvell QDEO on all accounts. Of course it's better than what a realtek player does (or what the old Sigma chips did), but it's still a joke for serious SD playback. A problem is also the 8911's scaling engine. It's soft and completely lacks any wow-factor. I would compare it to the Silicon Optix Reon, but probably not even that "good". I tried a number of SD DVDs, like SW Episode 4, Tarzan from the Warner Archive collection and a bunch of others and it wasn't great. Not even a hint of an "HD-look".
I had my Dune Smart connected at the same time, accessing the same network share and even there, the SD Images look *WAY* better. Considerably sharper and more detailed. Even when playing back 720p MKVs, the Dune's scaling was sharper and just nicer to look at. Of course the Dune totally sucks at deinterlacing, but what good is a nice deinterlacing mode (lacking a real film mode though) if the scaling doesn't cut it in the end ?
I think that most bugs will eventually be fixed and that the A400 will become a very popular HD media player with great app archive for online access to the popolar sites, BUT as of NOW and for ME, the 8911's VXP features are a total failure.