iTunes home sharing

I am trying to listen to music on my iPad 2 from my iMac. I have the iTunes home sharing connection set up but when I put my iMac on sleep the connection goes, is there any solution to this? If not does anybody know of any good iPad app that can remotely turn my iMac on and off and isn't too expensive?

Set your iMac to never go to sleep. Just set the display to sleep. Run my media box exactly this way.

If the Mac goes to sleep then you are toast as you found out. You could set a hot corner to turn off the Screen Saver/sleep.
Edit: Your specs say 10.7 - so that setup would be System Preferences -> Mission Control -> hot corners button at the bottom -> select disable screen saver. Bonus tip - you can select a modifier key so that you have to push the key and move the mouse to the corner for that hot corner to happen.

You could try netawake too - seems to work to wake on lan as long as you have that setup on your Mac.
NetAwake for iPhone, iPod touch, and iPad on the iTunes App Store

I tried using NetAwake but I couldn't work it out. The first option was best to make the display screen sleep so I've set a hot corner to do that, mixing both of your ideas. The only worry I have is that will having all of the processors and hard drive on in the background have a bad effect on the iMac? Overheating or the processor failing etc.

System Preferences -> energy saver -> wake for network access - needs to be checked for netawake to work. If that is checked then I am not sure why it isn't working.

You are using more power by not letting it sleep - so your monthly power bill will go up. As Bob mentioned, any computer that I use for media access - I leave on/no sleep - haven't really seen any problems. If it is just sitting there you won't overheat, disk access is also not that bad either. As a media server where it is just streaming media to various computers, pretty much any modern system won't be taxed at all doing that - i.e. very little stress to the system.

Preferably I would say it would be nice to be able to wake on network access to save some money/power. Also as you said - you probably want to have the screen blank so you don't cause any ghosting - but I leave on an old PC pretty much all the time - for the past 3 years.

I tried that through the help section on NetAwake and it didn't work for me, I will try it again in a bit when my iPad is charged up. I've set up a hot corner for sleeping the display so I can't see it being a problem then if what you said is right and it won't be very taxing to leave it all on, thanks.