Hi David and welcome to Beoworld.
Be sure that everybody here will assist you on their best to make a joyful first contact with B&O products.
Since you do intend to go for a linked system definitely you should go for either an Overture or a 3000. HOWEVER, my opinion would be to go for the 3000 (N.Music ready version) since this product will be very useful in your future link and as mentioned you will have the ability to distribute your digital music along with your internet radio all around the house.
Of course it's a bit more expensive than the Overture but for sure a better investment since it is not considered out of date product.
I will also agree on the speakers that it should be Beolab 4000 but if in any case you want to choose between 2500 and 6000 then my opinion is to go for the 2500 as there is no significant difference in sound between the two but only a big price difference and a matter of personal design taste!!!!!!
Feel free to ask and we are all here more than happy to reply!!!!
Once again welcome to Beoworld.
Best regards
Spiros