fair enough, what I have now is a bomb, and anything I buy now will be a slight downgrade (2ghz i7 quad, radeon6770, 8gb ram and 2tb).
Not necessarily. My late 2011 MBP 15" is similarly specced (2.5GHz i7 quad with 8M cache, 16GB, Radeon 6770 1GB, storage will be 2TB soon). The question is, what features/performance are you willing to trade off, what weight are you looking for, and how far that +- on your budget can stretch.
Since your location is listed as Seoul, I had a look at the
refub section on Apple's Korean site. Don't be scared by "refurb" - in Apple parlance it means eithe former shop demos that's had just about everything on it replaced, or stock clearance (more often than not stock clearance, but you can't choose what you get). You get the same guarantee, the only difference is it comes in a plain white box rather than the fancy pants packaging.
15" MBP Retina - ￦1,920,000 which is about R19K on current rates.
i7 2.3GHz Quad
8GB RAM
256GB SSD
Nvidia GeForce GT 650M 1GB
2880 x 1800 display.
What you'll give up is any chance of upgrading anything. The storage is a propriatary connector (at least, I'm not aware that they've changed to standard PCE-e), RAM is soldered onto the board, so there's no way of upgrading it. On the up side, battery life is pretty good, and the whole thing weighs about 2KG.
The 13" Retina is pretty much the same story, except it comes with a dual core i7, rather than a quad (and no BTO option for quad).
If you care about expanding the storage (for video you might), the 13" Unibody is the one to get, if you can still find them. It takes a standard SATA drive, and standard DDR3 RAM, and you can throw out the optical drive and replace it with an
Optibay or similar [1] caddy to put a second HDD in. So 2TB SSD storage is possible, so is 16GB of aftermarket RAM (exactly what I've done).
If you really want to go light, and the upgradeability limitations on the MBP doesn't bother you, then the MacBook Air is a good candidate. There is meant to be a new model on the way that has the high res Retina display, so it might be worth waiting for if you want higher resolution. The 1440x900 on the 13" is fine for me, but I find 366x768 on the 11" too restrictive.
Hope this helps!
[1] Be careful, there are
some issues with running SATA3 drives on the secondary controller, at least on some devices. It's not clear exactly what the problem is, and there are several
suggested solutions and posts claiming success.
Apple jokes aside, you are making a good choice. I also suggest mid specced 13" rMBP or the entry level 15" rMBP 
Enjoy!