It might be worth checking if they can upgrade the machine with an SSD drive. From what I have read over the last couple years, these SSD drives make a huge performance improvement, if you can afford one. You could keep OS X and your applications on the fast SSD and store the data on the "slower" regular hard drive.
Unfortunately, just too rich for me at the moment!
Btw the fact that this store can upgrade the RAM to 16 GB shows that it isn't an official Apple Retail Store. Apple offers RAM upgrades up to 8 GB total I think.
Not true, I think. I've bought several computers there, and they've always added locally sourced RAM at a fraction of the price of the Apple Store. But the rumor persists ......
As an aside, all the demo models in the shop had 16GB RAM in them. In particular, the 13" base MacBook Pro was screamingly fast!
Andrew (Brit expat in Taipei, Taiwan since 1985)