Yes, definitely go with Tumi, I have a full range of leather and ballistic bags. I'd go for the Generation 4 standard range rather than T3. T3 looks like it might date quickly.
Do not go for the 22" tumi, there's a good chance you will not be able to take it on board. My 20" only just fits in the overhead on a A32X so 22" is a non starter.
Regarding best place to buy, In the UK, you could try the Tumi outlet shop in Bicester Village near Oxford. Call them first to check if they have the 20" model.
In the USA prices are considerably lower. Better still, take a look at the prices on ebay.com, i.e. the USA site, there's plenty of latest generation stuff in leather or ballistic. If you have a USA trip coming up just have them deliver to your hotel.