Yes, it's a Blustreak in .20 - I like the .20 a lot as it has many of the shooting characteristics of the .177 (flat shooting, inherently accurate), but delivers just about the same terminal performance as a .22.
The set up I'm using on that rifle is a standard barrel clamp scope mount, the scope as you mention is a Tasco shotgun mount, I don't remember the model and it's not marked on the scope - but I bought it at Walmart for about $40.00. This scope has a long eye relief which allowed me to mount it as shown, more distal on the barrel. In advance of what I'm going to say next, an advantage of a multi-pump is that you can put a regular rifle or shotgun scope on it; unlike a springer which requires a specialized air gun scope to stand up to the bi-directional recoil these guns generate.
I like hunting with the Sheridan, but I've got a pile of air rifles including springers, PCPs, CO2, and multi-pumps. I don't know that if I was going to buy only one rifle that I'd go with a multi-pump. You might want to consider a springer (spring piston) gun, they are more powerful and are charged with a single cocking action-you could find one in your price range. Go online and look around before you buy - take a look at this site to get an idea of whats out there;
http://www.compasseco.com/catalog/ammo.htmlGood hunting!
Jim