A good lot for planets ect.. , anything 8" and over does a nice job. They don't give that much over a 10" but over an 8" they do. A 12" is a nice scope and you should get a ton of good views. Youtube and google images will show you the results, you really can't put it into words what you can see unless you were saying against planet A. and scope B., just as Stephen stated above. You have really asked the question of is a million dollars alot of money? To most people yes but a lot of others no.
Anyhow you should be able to see planets sharply and crsip, as for neb filters really help along with training your eyes
Anyhow google images and 12" telescope should show you what to expect for different targets
Really youtube videos would be alot better because your not talking about long exposures if you mean by see
same question but for an 8" here
http://www.iceinspace.com.au/forum/s...945#post884945