The Mossberg is a decent trainer, but if you want to get further than casual shooting it will limit you. SB events like 3 / 4 position and prone need a rifle with a degree of adjustability so that you can alter the rifle to YOUR position. Not the other way around. The Mossy might be alright for prone, kneeling, Varmint, maybe silhouette, (where you can use a scope), but it'll be a struggle to build a solid bone-on-bone position without some effort (and finding YOUR position is hard enough). Plus, if you move up and want to continue improving you'll
A) have to break alot of habits you've picked up as a result of using a rifle without the adjustability;
B) have to buy a new(er) rifle anyway.
A few events you may be able to do well with the Mossy, but building a position will be alot more work then it oughtta be.
As far as target rifles go, there isn't a whole lot of simliarities between the 144 and the Anschutz target line. Out of the box accuracy is exceptional, (as it is with Walthers and the Feinwerkbaus, among target rifles) and I'll be willing to bet better than the 144. The Sporter stocks offer a larger degree of flexibility for adjusting to YOUR position, the resale value is probably going to be better and even if you pick up a used rifle, it'll be in better condition than a 144.
Depending on the finances, I'd probably advise looking at an older target rifle or one of the Sporters vs the 144. It will probably be alot easier in the long run.
Scott
If we can get our schedules to line up, you're welcome to throw a few rounds through my Anschutz. Let me know.