Yes, you need to find UPnP Controller for Mac.
For example http://oss.linn.co.uk/trac/wiki/Kinsky is one of freeware. You can drag files to your UPnP device to play. Create playlist. Start streaming from UPnP server serources etc.
Hope this helps!
The Xscope mirror, a free tool works without needing VNC but you need a paid companion app on the Mac to send the data.
I prefer to use screens on the iPad. VNC is the way that OS X sends it's video remotely to another display. If you don't use it, someone else needs to re-write that entire stack and it works very well for local networks.
As for why the app I recommend, it has an observe mode and seems to scale the screen much better than the Xscope app since it is designed primarily for designing, not mirroring. The same program works on iPad, iPod, iPhone of all sizes and retina or not displays. It is very fast and has an observe only mode so that you don't accidentally send touch events.
If you do decide to use it on the go for remote access, there is a free location app (similar to how Back to My Mac works) and works over ssh tunnels if you prefer more security than speed. It has great soft keyboard support and of course works with Linux and Windows as well. There is nothing I can say bad about it in terms of missing features os bugs or design.
It's a quality piece of software all around.
If you really must avoid VNC, there is another option. The Xscope app for software designers has a free companion app that runs on the iPad and will mirror your screen. It's more designed for counting pixels and looking at mockups you design on the Mac for eventual use on the iPad, but you can use it as a mirroring solution. It lacks any input from the iPad and simply sends the screen from the Mac to iOS.
It also is very high quality software - and is well designed, all around and fast.
Best Answer
Plex Media Server offers "sync" functionality to devices if you have a Plex Pass subscription (starts at $3.99/month, less per month for longer subscription periods). You initiate the sync either from the Plex web app or device by selecting movie(s) to sync, and it then transcodes your selected media into a format appropriate for iPad. You then open the iOS app to download it directly to the device. See Quick Guide to Plex Sync for a run-through.
For adding torrents, the best solution I've found is to use Dropbox. If you don't already have a Dropbox account, set one up. Download the Dropbox client onto your server.
In the Mac menu bar, a new icon of an open box will appear. Tap on that, then tap on the folder icon to the left to open the Dropbox folder. Here, create a folder called "torrents" (or whatever you like).
In Transmission, go to Preferences > Transfers and set the Auto Add directory to the Dropbox directory you just created, which will be stored locally at /Users/yourusername/Dropbox/torrents/ or whatever you called it.
On the iPad, install the Dropbox client. Next time you want to add a torrent, act as if you're downloading it to the iPad. Since you can't actually download files to the iPad, the screen will change to show the filename, and will have a "Open in Dropbox" link at the top-right. Tap on that, then select the torrents folder you created in Dropbox. Tap Save at the upper right.
After a few seconds, the file will sync to Dropbox from the iPad, then from Dropbox to your server. Since Transmission is watching the directory where it will appear on your server, it will be picked up and automatically added.
There's a few steps involved in setting this workflow up, but once done, it's maintenance-free.