Hendrik can correct me if I'm wrong, but I believe Gizmo always transcodes.
You are also limited by Gizmo's quality settings (compressed MP3 audio and 720p video). From a quality, don't transcode perspective, you could try BubbleUPnP.
However, since both apps now support Chromecast, I see that as a better alternative for $35 vs $180 given the limitations. Especially when you can build an x86 HTPC as a Client in the $200 (Atom) to $300 (Celeron) range.
There is an old thread in the Android forum I started a while back (before Chromecast support) about this and the Neo 7.