The three mics in this thread are the ones i would have said, 57 421 and a royer 121. you can also grab a cascade fathead ribbon mic for less than 300 bucks and i have had great success blending it with a 57. The problem with dual micing is phase. You need to know how to place mics so they are in phase and how to hear if they are or aren't in phase. If you have someone to move the mics around for you in an iso room then dual micing is pretty standard and easy. if not, it becomes more time consuming and generally less worth it(depending on who you ask) Crooks knows what he is talking about.
your preamp choices are endless, my api pres sound great for guitars, my universal audio 610 sounds rad. unless you've got 500 bucks to spend on a preamp, learning where to place the mic will do more for you than an inexpensive pre. I can get perfectly good guitar sounds out of my stock mackie onyx preamps, entire records have been recorded using stock, run of the mill preamps, as long as you're not using behringer pre's you're probably doing ok.
I've heard great things come from joe meek preamps and you can generally find them in a channel strip with eq and compression used for 500 or so. sometimes less.