Recos for entry level Bookshelf speaker $400-750 for 21yo nieces first system?

I agree completely with freediver's recommendation of the Peachtree Audio deepblue2. I bought one for my daughter to replace the first system I got her, a Pioneer Elite amp, DVD/CD player and Usher 520 speakers. She and her husband wanted a simpler setup because their toddler was beginning to twist knobs and bounce off speaker stands and they, like your niece, were listening mostly to music from their iphones and ipads.

The sound of the deepblue2 is remarkable, I haven't heard anything better at anywhere near the price. The engineering and ergonomics are great and the simplicity and versatility sound like a perfect match for someone like your niece. For a young person who might be changing locations for a few years the ability to pick it up and move it so easily is a real advantage, and its size makes it easy to fit in almost any living space.

I was so impressed with it that I recommended it to some friends who seldom used their conventional system because it was stashed away in a cabinet and, like many other people, the easy access to music on a phone or tablet meant they simply weren't playing CDs anymore. Best part is, the deepblue2 sounds much better than their old system.

My advice would be to spend the same amount of money you were planning on but spend it on a deepblue2 and an iPad. She'll thank you.

Dali Zensor

I second the RS1 recommendation... but it all depends on what sound you are after at the end...
I have the rega RS5 (RS1 + naturally blended 7" woofer without crossover) and they are all about mid-range... clear, detailed, articulate and uncolored mid-range, with a hint of well extended quality treble and some well defined bass notes. Sound stage width and depth are so so, but they image very very well and seem to play all music genres equally well.  So I suppose the  RS1's voice is similar minus the re-inforced bass band.
The one thing lacking in the regas is the upper-bass band, and consequently they can become boring and fatiguing, especially with movies.  Even after the addition of a sealed subwoofer, I am still missing the smoothness and warmth of the vandersteen 2 CE sig I used to have.

So a couple weeks ago, I ordered a pair of Wharfedale Denton based on look, size, and the reported warm character and good reviews.  I was disappointed at first as they sounded horribly muffled with over-emphasized upper-bass/lower-mids.  After some 70-80hrs of play while I was out, better decoupling from stands,  better placement, and a comparison with the regas, they got a lot better and I finally could find them some qualities...
Their FORTE:  wide, deep, enveloping sound stage, fair imaging, good detail in the bass/upper bass (drums and toms sound really good), surprising dynamics, smooth treble, play 60s recordings like champs, even better with classical, jazz.. They are great with movies, they actually make you feel that a sub is unnecessary.  They are full without becoming boomy unless they are close to walls and heavy furniture.  The quality of the cabinetry is remarkable.
Questionable however is how much they color/muffle voices. They seem to do well from low-mids all the way down, but unable to deal with overtones and complex harmonics above that.  I do not remember the Vandys muffling that much.
Compared to another warm speaker I used to have, the PSB image t5, the Dentons are clearly a step up.  They are more detailed, and dynamics and soundstage are way better.  The PSBs muffled sounds a lot more as I recall.
The Dentons are clearly the kind of speaker I want to have on hand, even though I would prefer more naturalness in the mid-range... maybe they are not fully broken-in; they seem to take a long time settling-in.  And at $500?  Can't have everything done right.

Just my recent experience... Hope you find a great bargain!

A pair of Zu cubes would be nice choice. Easily driven, compact, and capable of playing loudly (she is a 21yo). And, not too much money.

ELAC  B5/6 or Unify 5 depending on budget, PS Audio sprout for a very compact system making no apologies at triple the 1-1.5 k investment...total!