I have no experience with Apple TV, but, it is certainly an option. Especially, if your media is sourced by and managed in iTunes. I am not sure if it very flexible with non iTunes media types/formats.
Another option is the
WD TV might be your answer. Its player is capable of picking up flies on local network computers and drives. Here are the formats it supports,
Video - AVI (Xvid, AVC, MPEG1/2/4), MPG/MPEG, VOB, MKV (h.264, x.264, AVC, MPEG1/2/4, VC-1), TS/TP/M2T (MPEG1/2/4, AVC, VC-1), MP4/MOV (MPEG4, h.264), M2TS, WMV9, FLV (h.264)
Photo - JPEG, GIF, TIF/TIFF, BMP, PNG
Audio - MP3, WAV/PCM/LPCM, WMA, AAC, FLAC, MKA, AIF/AIFF, OGG, Dolby Digital, DTS
Playlist - PLS, M3U, WPL
Subtitle - SRT, ***, SSA, SUB, SMI