I'm going to second the Lyman recommendation - though please understand that my comments don't have near the experience backing them as Captchee's.
The Lyman GPR is available in two twist rates - a 1 in 60 or 66 that is ideal for patched round balls and then a Hunter model sporting a faster twist (forget the actual rate) that is more appropriate for sabotted pistol bullets and heavier conicals.
If you want to add a bit of a personal touch, the GPR is available in kit form - the factory rifles look nice, but they appear to be built out of the kits - you buy the kit and fit the wood to the metal for an even better rifle.
Lyman also markets a Trade Rifle that is considerably cheaper and has a 1 in 48 twist that is an acceptable compromise for prb's and sabots. I own one of these and it is very accurate with about any round ball load and certainly acceptable with a 240 grain XTP or Cheap Shot bullet.
I scratch my head when I see people comment on how much easier an in-line is to clean. I pop the key on my Trade rifle, back out the nipple, set the breech end in hot soapy water and swab the barrel with a patch. The patch and jag draw water up in the barrel and things get nice and clean. I really like a large plastic Folger's coffee can for this task.
That's the traditional side of me - you need to get yourself one of those rifles (to start) and then:
There are so many decent in-lines available today and the 209 based primer ignitions certainly provide a more carefree ignition source.
Any of the ones listed above should provide a decent hunting tool, though they lack the character of a wood traditional rifle - even the ones like my Trade rifle that are not so historically correct.
I own two, and proudly hunt with them both - one being an older T/C Black Diamond that was one of the early "magnum" style rifles that hit the market. Magnum being capable of handling the pressures of 150 grain BP equivalent charges. That means very little to me, a charge of 100 grains eq absolute max has always met my needs.
This rifle has a fast twist - maybe 1 in 28 - that handles about any sabot or conical bullet on the market - maybe, but more on that later - and is scary accurate with a prb.
My second choice is a Savage smokeless model. Again, a fast twist that handles about anything (qualified) and actually does add some cleaning advantage over my sidelock rifle. The right load and bullet combination can produce tremendous accuracy and there are advantages to the increased velocity, etc..., but I'm of the camp that thinks those things are way over rated - particularly in the electronic world.
My accuracy qualifications above - really with all ML rifles - is that when you start dinking with sabotted bullets and such prepare yourself for a possible bad experience or two. If you do not have a combination that your rifle likes you may see results that will absolutely make your head spin and you might find yourself tightening stock screws, changing scopes, or whatever.
Don't start ditching hardware if you run in to that, try a different load combination.
I don't want to make that sound too discouraging - just be aware that it is a situation that you may run in to.
I always do initial sight-in on any ML with prb's, certainly easier loading and way cheaper to shoot. Once I get things dialed in where I want it and have some confidence in my hardware I start messing with load type.
Lot's of blabber on my part here, but it is a past time that I love.
I guess that if I wanted to get in at the overall cheapest today I'd buy one of the affordable CVA's or whatever listed above.
My real preference would be to start with either the Lyman GPR or the Savage, and then as quick as financially possible I'd add the complement. Then I'd have a reasonably priced fairly traditional rifle and a great performing modern ML at a reaasonable price.
I'd do the GPR 1st!
