Badmoth,
You can put together a great sounding amp/speaker combo purchased new for $2k as a place to start. I would look around a little bit and then just take the plunge. As you listen, learn and look around, you will get a better idea what your tastes are and what systems and gear people are listening to that is most likely to suite your taste. Then you can upgrade later if you get the itch.
I agree with much of the advice above - for classic rock you typically don't need the absolute lowest lows, but you do need adequate scale and volume without adding distortion. This does tend to favor larger floor standers and enough amplifier current to handle dynamic swings. I always say the hardest music to recreate convincingly at home is hard rock or a full orchestra.
No matter what you do, leave some money for decent interconnects and speaker cables. Reasonable wires are available from Internet dealers like Blue Jeans Cable, Signal Cable, while Auvio brand interconnects available from Radio Shack are actually quite good and Supra speaker cables from Sjofn HiFi also get rave reviews and are really cheap.
Here are my suggestions for amp speaker combinations:
-The all Rega system as suggested above with the RS5 speakers - perhaps look for used if over budget new
-NAD/PSB Image T65 as suggested (go with the bigger C-355BEE amp, or I would even suggest the C-375BEE which is 150W per channel and destined to become an audio classic)
-Cambridge Audio Azur 650A integrated amplifier and Paradigm Monitor Series v.6 model 9 floor standing speakers. This combination is guaranteed to sound at least as good as the NAD/PSB combination. The new Paradigm Monitor Series v.6 speakers are a revelation in this price range.
-Here is a somewhat unconventional set up, but I heard this combination recently and it sounded really good. NAD C-326BEE or Cambridge 550A integrated amplifiers and Vandersteen Model 1c speakers. This will provide a different and more open sound than the PSB or Paradigms, not quite as brilliant on top or forceful down low, but because of the recording style and quality of classic rock albums, the slightly warm and open delivery should work very well. Great speaker for jazz and vocals too. You can get away with less power with these speakers because they are relatively efficient (90db). I even heard the Vandersteen's driven by NAD's little C-315BEE and their higher end C-365BEE CD player and the system sounded great.
I am a big fan of the Cambridge and NAD amps and CD players. The NAD house sound is a little more laid back than the Cambridge which is a touch more lively and forward, although both are ridiculously good for the money. The same general rule applies to the CD players although here I slightly prefer the Cambridge models do to their incredible ability to suck information off your disks. Good physical set up with appropriate isolation from room vibration and the right interconnects and you will be amazed.