Recommendations for Kitchen System

I'd check out NHT which is an internet direct company and makes a bunch of really good speakers.  They are sealed and would work well for wall mounting.  You could pick up a pair of the absolute wall speakers for $400 a pair, add a stereo receiver (accessories4less sells manufacturer refurbished receivers from onkyo, marantz, etc), and you will come in well under $700: http://www.nhthifi.com/Home-Theater-On-Wall-Speaker-AWSB?sc=12&category=7166.  You may even have enough left in your budget to add a squeezebox touch so you can stream music and/or listen to internet radio stations.  If you are starved for space, there are a couple of CD receivers that allow for internet streaming like the Teac CR H500NT (although this would be a budget breaker at $600), http://www.amazon.com/Teac-CR-H500NT-Stereo-AM-FM-Internet-Receiver/dp/B0040Z0CIQ/ref=pd_sim_sbs_e_2, or the Onkyo TX 8050 which runs around $300 but you'll need a usb dongle for it (or connect it via ethernet).  I was actually thinking about getting a cambridge soundworks for my kitchen but I'm having second thoughts after reading your post. 

Edit: I just re-read your post and realized you plan on streaming via an apple express.  The analog output from the express frankly doesn't sound that great so get a receiver with digital inputs.  The least expensive one I know of is the Onkyo TX 8050 ($300 from Amazon, less from accessories4less) and you obviously won't need the usb dongle with the express.  The NHT absolute wall speakers and the Onkyo TX 8050 will pair nicely together and run you $700. 

That makes sense with the radio.  Btw, the HK 3490 runs a little less than the Onkyo TX 8050 and has digital inputs as well.  The HK 3490 is a more powerful amp spec wise but the Onkyo is plenty powerful enough for the NHT speakers and does a better job of integrating digital inputs (you can directly connect a hard drive or an ipod via usb, it has multiple digital inputs, and I believe (you'll have to read the manual) that you can switch seamlessly between digital, the tuner, and analog (I'm pretty sure that the switch is not quite so seamless with the HK 3490 as it has to be done manually)). 

Check out ascend acoustics htm-200 SE speakers; they're designed to be wall mounted as well: http://www.ascendacoustics.com/pages/products/speakers/htm200/htm200.html

Also check out Axiom audio which is another internet direct company that has a few different on wall models: http://www.axiomaudio.com/index.html

Amps depends on what you require from an amp, receiver with loads of inputs , http://www.amazon.com/Harman-Kardon-HK-3490-Receiver/dp/B00198F89A/ref=sr_1_1?ie=UTF8&qid=1323956162&sr=8-1 , small t-amp http://www.amazon.com/Dayton-DTA-100a-Class-T-Digital-Amplifier/dp/B004JK8BDK/ref=sr_1_2?s=electronics&ie=UTF8&qid=1323956242&sr=1-2 , basic power amps http://www.amazon.com/Dayton-Audio-APA150-Power-Amplifier/dp/B000VKXLBO/ref=sr_1_1?s=electronics&ie=UTF8&qid=1323956297&sr=1-1 , http://www.amazon.com/Samson-Servo-Stereo-Power-Amplifier/dp/B000QCJR4W/ref=sr_1_cc_1?s=electronics&ie=UTF8&qid=1323956314&sr=1-1-catcorr , http://www.amazon.com/Behringer-A500-Reference-Class-Studio-Amplifier/dp/B000KGYBQI/ref=sr_1_1?s=electronics&ie=UTF8&qid=1323956333&sr=1-1 .

Speaker wise you would be better off going to a local hifi shop of somewhere and demo some speakers first, since you want to wall mount avoid anything thats rear ported, and if you want to fill the room with sound and since your wall mounting above ear height avoid anything thats directional with poor off axis responce that rely purely on placement.

This behringers would do the job http://www.amazon.com/Behringer-B2030P-Ultra-Linear-Reference-Monitor/dp/B000N94S7O/ref=sr_1_1?ie=UTF8&qid=1323956655&sr=8-1 , http://www.amazon.com/Behringer-B2031P-Ultra-Linear-Reference-Monitor/dp/B000LQ2ABK/ref=sr_1_1?s=musical-instruments&ie=UTF8&qid=1323956955&sr=1-1 , you'd have to wall mount them on stands but there be fine because there front ported.

All the speakers I recommended are sealed and designed to be wall mounted.  They are also all internet direct manufacturers that provide a 30 day money back guarantee.  They NHT speakers are very, very good; the other 2 manufacturers are very well considered in the business and I would not hesitate auditioning either the Axioms or the Ascends.  Insofar as the amp is concerned, the OP wants to use an AE express and should get, therefore, a receiver with digital inputs, the obvious choices in his budget are the Onkyo TX 8050 and the HK 3490.   There are trade-offs to both as I mentioned in my first post. 

Can also get a seperate dac theres loads to choose from , http://www.amazon.com/FiiO-Digital-Analog-Audio-Converter/dp/B0053VKP8S/ref=sr_1_1?ie=UTF8&qid=1323961664&sr=8-1 , http://www.amazon.com/Musical-Fidelity-MFVDAC-V-DAC/dp/B001P6FO5E/ref=sr_1_1?s=electronics&ie=UTF8&qid=1323961675&sr=1-1 , Them receivers are quite large so if space is issue a small t-amp and a seperate dac would be more suitable, no trades off have to be made there are plenty of options and thats what I was pointing out.