Setting up wireless digital music server

I am interested in putting much of my music collections to digital and control with an iPad. I have an inwall speaker system (and HT and 2 channels). The inwall speaker system would be the main target, but I also would like to access to the digital music library from other systems (plus on my laptop via wireless). Currently I use an integrated tube amp to connect to the inwall speakers.
I have mp3 files stored on a wireless hard disk. I don't have an iPad yet, but I will buy one and try to convert those mp3 files to iTunes library, and use the iPad screen to browse and select music. But I am not sure what other options are available for the rest. I might need to replace the int tube amp to a digital receiver that can connect to the wireless music server?
Any suggestion?
A Mac mini plus an external DAC. The iPad will control iTunes via the Mac mini.

USB from the Mac mini to a dac of your choice. DAC via analogue RCA jacks to you integrated.
A simple Sonos system could work also if you want to keep your music files on your current hard disk. Add a DAC and you should be good to go.

***Sonos dealer disclaimer

Goldprint Audio
I was in a shop the other day and saw that Marantz now has a networked player component of some sort. Have not had a chance to investigate the details though. That shop also sells Sonos stuff.
I wonder now if the trend will be that the mainstream audio vendors like Marantz and others (including specialty digital high end vendors) will be the ones that provide the digital source player components for home hi fi down the road that replace those that have gone by the wayside in recent years (Roku, Logitech)?

That would seem to make sense. These vendors need to keep with the times and not let the CD medium dropoff affect them. Designing and selling the next generation gadgets that enable one to play modern digital sources like internet and music server on ones system seems to be the ticket. After all, no hifi music without a digital source these days. I know there is always vinyl but I do not expect that to ever be more than a niche technology for some moving forward. Ipods and portable players alone will not cut it.
Thanks for reply. Looks like it is simpler than I thought.
Mac Mini Plus would be nice, but I want to try Sonos solution. At the moment I am not worrying too much about the sound quality. For serious listening I can use my BAT vk60/vk30 with Tyler speakers. (I don't listen to digital music that much, mostly vinyl with BAT ;-)
So, with Sonos, I only need to purchase a Sonus Bridge and Connector, about $400 in total. Since the Sonus connector has an analog output I would not need a DAC, well at least until I feel bad about its analog output sound quality.
Then, I can use my iPhone or iPod touch to control the music until I get an iPad.
I also see wireless receivers (amp + tuner) are coming to the market). The receiver can recognize music files stored in a wireless hard disk. But I am not sure whehter they support controls from iPhone/iPad.

Many thanks for your input.
Pioneer VSX-1122-K is a multi-channel Network Ready A/V Receiver. The spec says iPhone, iPod, and iPhone can work as a remote control.
This may be a trend in the coming years. Customers may look for wireless network connection to music server as one of the key features in AV receivers, as they look for SmartTV feature in flat screen TVs.
"The spec says iPhone, iPod, and iPhone can work as a remote control."

BEing able to use a remote controller like this or even just a PC browser is a key feature for me. That provides the most remote control flexibility and also the most flexibility for displaying album art and other types of related content that might be available on the internet.

A trend will be for devices to get better at making it easy to navigate to internet content to look at while listening. This will hopefully move things forward again in terms of overall experience with recordings that took a big step back when tiny CDs replaced larger lps and the extensive album art and other content that used to often be included.
Another vote for Sonos.

**** Sonos owner and loving it disclaimer! :)
I use a Sonos for the same purpose. It is easy to use and works great.