My system is lovely and I am very happy with its sound.
Krell 402e, BAT Rex preamp, Esoteric K-01 CD/SACD player, Revel Salon2 speakers, Stealth Indra and Siltech cables.

Here is the question: I want to be able to play music from a iPhone or a laptop, etc., for when I am entertaining and want a playlist or just a long selection of music. I don't want to have to play CD after CD. This is merely for listening with people over for dinner, cocktails, etc.

The sound from the system fills the house no problem. I know that the Esoteric has the ability to use its DAC with an external digital source.

What is the best/easiest way to solve the problem?
I don't want to make the switch to a server as my sole source. I also do not ncessarily need to listen to hi-res files only. There will be a mix of music from my phone, my daughter's phones, other phones, etc., plus I may want to build a couple of playlists on an iPad that are a bit more specific (jazz only, pop only, vocals only, etc.). Those playlists could be hi-res or not. But as I said before this is for non-critical listening.

Which pieces do I add to the system, what cables do I need?
The simplest way is to get a Sonos ZP-90 and a Synchro-Mesh to reduce the jitter. It is connected computer -> network -> Sonos -> Coax or toslink -> Synchro-Mesh -> coax -> Esoteric. You can drive it from most computers and other devices.

Cost is $400 for Sonos and $600 for Synchro-Mesh

You will be disappointed in Sonos by itself.

Another option is the iphone plugged into a Pure i20 digital docking station to Synchro-Mesh to Esoteric.

Steve N.
Empirical Audio
For your minimal needs something on the line of bluetooth options may be a good bet. Products from Audioengine, Arcam, NAD and Xantech etc. Simple connection to stereo via RCA line outputs to stereo. a good place to start your research.

Great to be able to control the music from your easy chair or from anywhere across the room. Decent to good sound and it won't break the bank.
The simplest is to plug the ipod/phone headphone out into an aux input on the pre. use one of these. It'll sound fine for your needs.
Another solution is the NAD dac1, cost $200. Its available everywhere like best buy, crutchfield, audio advisor, etc... It's a wireless system with a small transmitter that plugs into your Mac/pc via a USB cable, the other component, the receiver, has both line level and digital outputs. It's a very simple set up. Requires no software, other than iTunes or whatever's native to your computer. I have one connected to my CD player via the digital out and it works well.

Do a web search and check it out.

Note: you can go nuts trying to select a digital cable. From the reading I did whatever cable you do select make sure it's at least 1.5M long. IMHO - it did make a difference.

Good luck
Given your needs, I would go with Timrhu's recommendation. Its simple and it costs almost nothing. If you don't like it, you can always upgrade.
You can buy an Apple TV for $99 and connect it via optical to the esoteric. You can then stream music directly from any apple source directly to the Apple TV. Also if your laptop is windows you can get the MOG streaming music service which will allow you to stream from a non-apple laptop or android phone. This is likely the cheapest and easiest method, and since it is for non-critical listening the quality should be decent enough for background music while people are talking.
Man, I had the same thing going on at my house for New Year's Eve. I have a Sonos, a Squeezebox Touch and an AppleTV. We wound up using the AppleTV a lot that night because it was a simple matter of either playing music from files on my NAS, MOG or even directly off of guests' iPhones via AirPlay.

Given your use, and audiophile standards aside, I'd say check out the AppleTV. What was really cool was that many of my son's friends had music videos on their phones and they were able to stream them to the stereo and TV via AirPlay.

When I just want to run a jukebox type of thing, either the Sonos or Squeezebox will do, using an iPad as a controller that I leave out so that guests can add to the play list from either my library or MOG.
Where the Hell people get the $$$ to buy this over priced equipment , How about the new Rogue Sphinx intergrate ?It already put China out of buiness .
If you have or can put music on your PC and have a network use JRiver. You can download the app JRemote for you IPhone use it as the player device or remote to play music from your computer to a dac device. You can also use JRiver to play music on your laptop to its own speakers. Cost is minimal but your music is with you everywhere. You must open port forwarding on your network to use it everywhere you go but that is the hardest part of the setup.
Also look into a program called Subsonic Music Streamer it's free. It coverts most network music files on the fly to MP3's and there are Apps that connect to it. I just started setting up this program so info is limited at this time. I figure if you want music from your IPhone you are not looking for high quality.