Supakit:
We can't really answer the "sound" questions as posed, exactly, because it's so very dependant on what gear you're actually using. Speaking VERY GENERALLY, though, the tube amp will give you the full "tube sound" right from the start, with either a ss or a tube pre. A tube pre may give you much of the smoothness and musicality of the tube treble and midrange, without sacrificing much detail and bass "punch", when mated with an appropriate ss amp. Neither is necessarily "the better approach" - it completely depends on what type of sound you want. Since you emphasize detail, I'd probably suggest the pre-amp first, but you'll find advocates for both approaches. Note that pre-amps generally use fewer and less expensive tubes, which can be a consideration when buying used.
The last question is a stumper - almost any tube pre or power amp is great for that kind of money ;) Right now, just on this site, there's a Dynaco ST-70 for $250 (a venerable amp with a bazillion upgrade options and a huge knowledge base available to consult); a Moscode 600 hybrid for $600 (I have a 300, which needs attention but still makes lovely music, in their day these were wonderful bargains and to my ear, still are); a couple Anthemn Amp 1s and Jolidas on the lower end, not to mention some QuickSilver Monoblocks in the $900s. For pre-amps, there's an ARC SP-14 for $900 (ARC makes good stuff, though I don't know the SP-14 at all); a Conrad Johnson PV-10a for $650 (nice unit with phono stage); and several QuickSilvers, other CJs; etc. Personally, I'd go with the PV-10a to start out, it's a reliable performer with a nice sound and a good resale (important when you want to upgrade!), but I look forward to the other answers you'll get as I know there are far more experienced tube-o-philes around. Good luck!
chas
We can't really answer the "sound" questions as posed, exactly, because it's so very dependant on what gear you're actually using. Speaking VERY GENERALLY, though, the tube amp will give you the full "tube sound" right from the start, with either a ss or a tube pre. A tube pre may give you much of the smoothness and musicality of the tube treble and midrange, without sacrificing much detail and bass "punch", when mated with an appropriate ss amp. Neither is necessarily "the better approach" - it completely depends on what type of sound you want. Since you emphasize detail, I'd probably suggest the pre-amp first, but you'll find advocates for both approaches. Note that pre-amps generally use fewer and less expensive tubes, which can be a consideration when buying used.
The last question is a stumper - almost any tube pre or power amp is great for that kind of money ;) Right now, just on this site, there's a Dynaco ST-70 for $250 (a venerable amp with a bazillion upgrade options and a huge knowledge base available to consult); a Moscode 600 hybrid for $600 (I have a 300, which needs attention but still makes lovely music, in their day these were wonderful bargains and to my ear, still are); a couple Anthemn Amp 1s and Jolidas on the lower end, not to mention some QuickSilver Monoblocks in the $900s. For pre-amps, there's an ARC SP-14 for $900 (ARC makes good stuff, though I don't know the SP-14 at all); a Conrad Johnson PV-10a for $650 (nice unit with phono stage); and several QuickSilvers, other CJs; etc. Personally, I'd go with the PV-10a to start out, it's a reliable performer with a nice sound and a good resale (important when you want to upgrade!), but I look forward to the other answers you'll get as I know there are far more experienced tube-o-philes around. Good luck!
chas