Simple Question. Duo to sony & panosonic

I would hazzard a guess that it can.
I myself use 2 x readynas duo v2's an a v1 to a sony Sony BDP-S370 Blu-ray player and a Sony BDP-S380 Blu-ray player.
Both work perfectly streaming almost everything i throw at them.
Just avoid firmware 5.3.6 on readynas duo v2 as it breaks the dnla server.

As for twonky, ive no idea. I have never had a need for anything else as it worked fine as is.

I have a ReadyNAS Ultra6, I got a Sony BDP-S390. Worked great for one night, I was able to stream .mkv and .mp4 without a problem. Then i upgraded the firmware on the BDP to v M11.R.0422 (they force you to if you want to use Amazon Instant Video or Netflix) and now every video I try and play says "The File is corrupt or not supported". Sony always forces you to upgrade, i knew this and thought twice about purchasing it, i should have avoided the Sony. Also the updates take forever, had to try 3 times and ultimately left it over night to complete.

As with any firmware upgrade, sometimes things dont always go the way we hope an in your case it would appear sony have removed or broken support for some file types. I recall this happened with my S370 too but it was corrected with the following firmware update so not a big issue as this can happen with any makers devices (as recent dlna with duo v2 has shown) Your best bet to be sure would be to post on the sony support forums.
As for the upgrade, i have to say having had sony tvs an bluray players, media players an playstations for many many years ive never had an issue updating, the bluray players an tv usually take no more than a few mins to download and install new firmwares. Its highly likely the problems you mentioned are caused by other factors such as internet routing, connection speed. It is worth noting that if you are having issues downloading firmware directly to the device you can download them manually an install them manually.