I suggest you look into either Roku 3 or a WDTV Live. AFAIK both support DLNA. Haven't done much w/ Serviio personally, so I can't comment on what you might expect by comparison.
I have a home tetwork set up that consists of desk top which is hard wired and has an external hdd which contains all my movies. The pc is on all the time and runs serviio media server. My main tv in the house is hard wired to the network and I can conect and stream movies from the external hdd by selecting serviio from the input selection menus on the tv, from there I can browse through the folders on the hdd and select a movie to watch.
My question is. The tv I have in my bedroom does not have an Ethernet port but does have HDMI and USB what would be the best device to use to connect this tv to my home tetwork via wifi that will allow me to brows through the files on the hdd and select which movie to stream from the tv ? Apple TV ? Roku ? Chrome cast ?