I'd like to add, that if you want the best audio quality, avoid turntables and passive speakers. LPs are really crap audio wise (smashed stereo image, signal to noise ratio, static, booming etc.), avoid tube amps which is in the same realm of hyperdistortion, and last but most important for the most of us, do not choose passive speakers or "powered" (i.e. they have a passive crosssover but have an inbuilt amplifier). Choose some well built actives.
As for size, well it depends what you want to use them for. Big passive threeways usually gives you "boom". although small passives can do that too ("boom" is not bass, it's a booming speaker, and you have probably heard a few of those).
I use small speakers for my near field monitoring. They're active, and if I recall correctly, Dave M. uses small speakers as well.
For more bottom level, yes it might be an idea to invest in a sub, but I don't need a sub for my near field monitoring needs.