You know, for someone who claims to know so much about this, you really don't.
Bookshelf speakers are simply speakers that can be placed on a bookshelf and played from there. The interesting thing is that bookshelf speakers don't sound so good on said bookshelf, and are best placed some distance away from walls to get the best sound out of them. Example below:
KRK Rokkits are powered monitors, mostly for mixing purposes, but are also good because they reproduce the music pretty accurately. I bought a pair of the KRK Rokkit 6's for my brother, so I know what they are. They are similar in shape and size to the bookshelf speaker I have linked above. The difference is that the KRKs are powered, and the one I linked is passive and must be connected to an amp of some type.
And yes, a standard bookshelf would carry the weight of KRK Rokkits. With all the weight of the books that it normally holds, 40 lbs in speaker isn't that bad.
I have ALREADY explained that I had agreed with you in that he should be going for a nice 2.0 setup, and not a 5.1 setup. Again, you're the dumb cunt that has failed to read my posts. At first, you had misread my post to think that I suggested that he go with a 5.1 setup, and then you failed to read my last post where I stated you misread my first post (and I further explained myself there). Maybe you need to take some time instead of skimming.
Whatever the budget may be, a dedicated 2.0 system will always be better than a 5.1 system for music listening.
Moving on. I provided a link for a relatively cheap (and based on the reviews I've read) and good sounding amp that would be ideal for a desk or similar. This can be paired with an unpowered pair of BOOKSHELF speakers of his choosing and complete the system. OBVIOUSLY, he can find another stereo amp of better caliber and use that instead.