What you need to do is go out and listen to as many speakers, and as many types of speakers, as you can stand to audition, that cost less than about $1700. Leave your money, checkbook, and credit cards at home; you should not buy until you have listened to many things in many different stores.
How much you can spend on your speakers will depend upon how many types of sources you want, and on the characteristics of the speakers (as low impedance and inefficient speakers require better amplification). But speakers will make the most difference in the sound quality of your system. Scrimp on them, and everything will suffer for it.
No. They are a total waste of money if you want accurate sound. Tube amplifiers distort more, and some people like the sound of added distortion. (See the links below in connection with turntables for more information on the idea of people liking distortion.)
That depends upon what else you are using. Most likely, it will be more cost effective to buy a receiver than to go with separates, but it really depends upon what speakers you end up with.
No. CDs, if well made, can sound extremely good. Some audiophiles like the sound to be altered and less perfect, so they prefer things that add distortion, like LPs. See:
http://www.hometheaterhifi.com/technical-articles/426-a-secrets-technical-article.html
http://www.hometheaterhifi.com/technical-articles/427-a-secrets-technical-article.html
Before CDs came out, digital recordings from the late 1970's and early 1980's that were put on LPs were thought to have great fidelity. It is only after people were able to eliminate the added distortions and imperfections of LPs that people started to object to digital. They were used to distortion, and they missed it.
No. Wires are one of the biggest scams in audio. Read this:
http://www.roger-russell.com/wire/wire.htm
CDs will give you better sound than any turntable, provided that they did a good job making the CD (which, however, is not always the case). However, since your father is planning on giving you his old LPs, if you want to play them, you will need to budget for it. If you want to listen directly to the records, you should just go analog. But if you want to process the sound to eliminate clicks and pops with your computer, and put them on CDRs, then you might want to go with a USB turntable. I personally would just forget about a turntable, but you must decide these things for yourself.
If your father is getting rid of his LPs, is he also getting rid of his old turntable? If so, you might want to just use that.
I cannot stress too much the importance of speakers. Spend your money there, and you can go with a very inexpensive CD player, and probably a very inexpensive receiver. No speaker, no matter how expensive, will have a frequency response as flat and perfect as an ordinary inexpensive CD player or an ordinary receiver. And the speaker will distort much, much more as well. So spending your money getting a better speaker will matter far more than any difference among CD players or amplifiers (assuming that the amplifier is adequate to drive the particular speakers in question).
One last thing: There is so much BS spread about audio, that it is difficult to avoid. Don't trust anyone, including me. Research these things, and believe only what seems reasonable to believe after looking at a variety of opinions and thinking very, very carefully about it all.