Graeme - to expand on David's note, the main reasons I've heard cited to pick up the 4308 versus the 3808 is the wireless internet and/or HD radio capabilities (or the 10 watts per channel, which is so minor that it's unlikely ever to make a significant audible difference for you)
If these few additional features are important for you, then it would be a good purchase for you over the 3808. If not, even if the "deal" on the 4308 is better than the normal price you can get on the 3808, you might be paying extra money for feature upgrades that you won't get any benefit from. If the deal you've found makes the 4308 cheaper than the prices you can get on the 3808 where you live, then by all means, I'd snatch it up in a heartbeat.
I believe you'll be very happy with your choice either way.