There is a whole new range of "entry level" rifles now that will meet your needs. The Savage Edge, the new Ruger All American, The Mosberg ATR, or is it 4x4?, Maybe the new Rem 710?
I'm still undecided on the Ruger American it hasn't been out long, but the Rem 710 probably hasn't been produced for around 10 years now, and Savage had to change the name from Edge to Axis probably due to copyright infringement. The Mossberg is still out there but not a rifle I'd buy, I don't know if they fixed the bolt problems or not, but I don't want one.
If you are looking for a rifle you can improve over the years as your shooting skills improve then I'd throw out the Mossberg, Savage Axis, Ruger American, T/C Venture, Marlin XS/L-7, and the Rem 770. There just aren't options and probably never will be to upgrade much on these rifles as you go and money improves. I doubt you'll see a lot of companies out there trying to offer aftermarket options for most of these rifles.
Rifles you can upgrade as you go are the M700 ADL, Stevens 200/Savage 10/110, and Howa/Weatherby Vanguard. The M700 is probably the most used action or cloned action for most of todays custom Target/Tactical builds as well as a lot of hunting rifles. The 700 has the most aftermarket parts for it and a lot of Gunsmiths earn there bread and butter on this action.
For the DIY kind of guy there are nothing better out there than the Savage/Stevens actions, but there aren't as many aftermarket parts for them. Savage likes to change thing up quite often and it takes awhile for things to catch up. Howa/Weatherby has probably the least amount of aftermarket options for it but far more than most entry level rifles.
The thing about all these rifles is they start in the upper $300 and can be had for less than $500 most places. If you watch for deals sometimes the Stevens 200 will be around $250-300 and the Savage 10/110 for right at $400. Wal-Mart has the best prices on the M700 that I know of, with tax you'll be out the door for around $450.