TC problems with NAT

Would really appreciate some help guys/girls.....

My Kit
MBP unibody 15inch 2.66 - wifi turned on

Time Capsule - for home wifi network and connected to BT modem/router (wifi turned off) - i.e. used as the ADSL modem only

WD world Book (used for itunes / network hard drive) - plugged into TC

Airport express with airtunes
Xbox360 wired to AExpress
Bose stereo also wired to AExpress for airtunes

PS3 wifi connection to network

My Problem
There appears to be a problem with my NAT? I am not sure of the problem exactly, as I never had it with the less complicated modem/router. Essentially it slows down the network considerably meaning that I can not use airtunes as the music keeps stopping and starting and nor can I connect to the internet with the xbox. Also the general speed of the network is pretty rubbish.

My i.p. address is a 192.168.XX.XX type not 10.XX.XX.XX
Am using DHCP to autoassign etc

Any help will be greatly received

Thanks
Ben

 

Sorry to rehash this myself - I know it isn't really the done thing, but surely someone has had this problem and solved it?

It makes most things unworkable at the moment

My xbox360 cant stream my sky

My Airtunes stopped and becomes erractic 20 seconds into a song

Any help much appreciated

 

Cheers

Sorry for delay in replying - in response to question

BT box is in bridge mode via a downloaded config BeBox

I have the TC cabled to it, I then have two airport extremes both of which are in joined network state.

1) Attached to speakers
2) Attached to DLNA compatible TV - so I can use my NAS hard drive movie collection.

I still get so much stuttering that am thinking may sell it on ebay and buy a Sonos......

Not sure buying my ATV v2 was such a good idea now either.....