Most Major NAS Suppliers Can Do what you want
I run in different locations:
QNAP TS109 to Buffalo Linktheater, PS3 using Twonky 4.4.4
QNAP TS409 to Netgear EVA8000 (SMB), XBox 360 and Terratec Noxon 2 (Twonky 4.4.4)
QNAP TS201 to Netgear EVA8000 (SMB), Philips Streamium (Twonky 4.4.3)
Thecus 5200B PRo to Netgear EVA8000 (SMB); Sonos (SMB); PS3 (Twonky 4.4.4); XBox 360 (Twonky 4.4.4), Philips Streamium (Twonky 4.4.4)
QNAP TS-209Pro to Philips Streamium (Twonky 4.4.4); Sonos
The QNAPs come with Twonky but you have to wait a bit for the latest release in the standard firmware (a long wait for the TS-201). The Thecus is a package install of Twonky which is simple (similar to the Twonky install on the ReadyNAS).
All devices can also have Slimserver installed on them although if installing both Twonky and Slimserver the ports must be adjusted.
For streaming I prefer Twonky as it has a better tree structure. If streaming video to a PS3 and running subtitles you will need to combine the subs with the movie but there are quick non destructive tools to do this.
Basically any of the significant NAS suppliers (Thecus, QNAP, Netgear, Synology, Raidsonic etc) can do what you are after. Beyond that you are into manufacture loyalty and individual preference. Except for the small Raidsonic device the performance is pretty much the same. Cost per Terabyte is also within a comparable range. Obviously 2 disk units are more expensive per terabyte but the difference between 4 & 5 disk units is marginal with multiple units if you install the disks yourself.