Which Speaker

I have a friend with a Yamaha A-S301 integrated amp and some Monitor Audio Bronze 2 bookshelfs and it sounds very good. He added a used SVS sb1000 sub and the overall sound quality surprises me every time I hear it.

I also have another friend that had Kef Q700 towers and a mid tier Marantz AVR and I was always impressed by the Kef Q series. He likes to listen pretty loud at times and the Kefs did a good job of keeping up. He upgraded to Monitor Audio Gold 200 towers for what its worth. 

Lots of good options for a first system in your list. Set a budget and stick to it. Resist the urge to upsell yourself chasing the opinions of others. There is always a step up the cost ladder available with hi-fi gear and always someone here ready to tell how much better it could be if you just spend a couple hundred more.

Its usually larger drivers or more drivers as you work up the model line. For example, the monitor audio silver 50 is the smaller bookshelf with a 5.25" driver while the silver 100 is the larger bookshelf with an 8" driver. Try looking for pictures of the entire model line together (most manufacturers do this) and it will help with perspective as you can see the relative size difference between the speakers in that model line.

Also, if you do go down the upgrade rabbit hole as many of us have, your perspective will change regarding price and value in general. When I bought my Rega Planar 2 a couple years ago, $600 was what I considered my max budget for a turntable. Earlier this year I bought a new model Planar 8 with Apheta 3 cartridge and a Rega Aria phono stage.  All together that package retails at about 10 times the Planar 2. I've done similar things with speakers/subs/cables etc. I don't regret any of those purchases but it was a process to get there.

You may find out you are quite content with your initial purchase and never get the upgrade bug (as my pal with the yamaha/ monitor set up is) or you may go full crazy like the rest of us.  If you take care of your gear you can always trade it in (save your boxes).  Used stuff didn't start appealing to me until the prices started getting higher. On a $5000 pair of speakers you can be pretty sure they are in good shape from a good reputsble seller and the 40% discount makes the purchase easier to justify. On entry level gear I tend to agree that new is the way to go not enough benefit versus the risk.

Good luck and keep asking questions if you have them.  Lots of knowledge people here on the forum.

Only vintage speakers can play rock music?  That is a first for me.  Guess I need to dump my Revels...