Cellular phone and speakers?

Background is the best you can get out of iPhone w/o an external DAC. Go for it.

The point here is to use my bookshelf speakers with an iphone .

The iPhone doesn't have binding posts to connect to speakers. I'm not sure if you can add binding posts to the iPhone with suitable accessories. Best bet is to add a small shoebox amp.

You need a small amp of some sort and using one with Bluetooth built in or get a Bluetooth adapter to stream from you iPhone to the amp, which then powers your speakers. The iPhone does not have enough power to drive those speakers, so you have to find the room to fit an amp of some kind.  I use an old iPad stream to an old NAD receiver in my work shop. It’s fine for background music, you can check out the PS Audio amp “Sprout” to get the idea and you might find it small enough to fit someplace . I do not own one, just giving you the concept. 

I second deadhead.  At the bare minimum you need an amp and a device that can accept either Bluetooth, AirPlay, or Chromecast, which are the wireless ways to send music.  Are you  sure that you can’t clean out some of that stuff to make room?  My suggestion would be to get a pair of speakers that come with a Bluetooth receiver and amp built in.  My suggestion would be Audioengine.
Later after you clean out the space a little, and if you really want to use the VA speakers, I would by a small integrated amp that includes a device that can receive one of the three technologies listed above