They all uses the same V2 board.
IA-7 V2 - very costly to make and we rather that you don't know about it

. 85% (or more) of the performanhce of P8 + Ref 9 V2. BUT, it has limited power: 100W x 2. So, you pay much lower price because of the compromised performance in an integrated amp, lack of upgrade path, and we really cut our margin to the bone to attract entry level Nuforce customers so hopefully one day you'll consider other products.
All consumer companies use similar marketing technique and product positioning. Nikon has D200, D80, D40X, etc all based on the same platform. We all know we pay a premium for top of the line product (I bought D200 because I can afford the extra premium and I am a sucker

). The more you go up the performance curve of Porsche 911 line, the more premium you have to pay.
But customers are not cow for milking. We need to justify the performance and benefit. So for 9SE, we charge less for the upgrade and offer 5 year warranty instead of 3. If you consider the 10 year ownership of Nuforce, assuming typical audiophile will trade equipment 3 or 4 times (during the period), the long term cost of ownership is much lower when technology upgrade is taken into consideration.