I can recommend the CMStorm line of mechanicals as affordable but good quality boards and most of them have a standard layout so you can replace the keycaps easily, which is one of the best perks of owning a Cherry MX keyboard IMHO.
I would also recommend Browns as a starting point. They're "tactile", meaning the pressure as you press increases for a bit, then suddenly decreases as you go over the "bump". Blues are "clicky", so they have that tactile bump, but after the bump the force descreases even more rapidly and they make a click sound. Reds and Blacks are linear, meaning they just have a spring and no tactile bump, the resistance just increases slowly as you press the keys. Blacks have stronger springs than Reds, Blues and Browns.
All Cherry MX actuate in the middle (around 2mm) of the slider movement (4mm), whereas your K120 and other rubber dome and membrane boards actuate at the bottom of the movement. On Browns and Blues this is just after the tactile bump. Lack of tactility means you can't feel when the switch actuates (Reds and Blacks), so it's easy to mistype letters, especially on the lighter Reds.
Hysteresis is where the reset point of the switch is different to the actuation point. All the "clicky" MX switches have this. It means you have to almost completely release the key before you can actuate it again. With Browns, Reds and Blacks you can "hover" the switch around the actuation point for faster response in FPS games, for movement keys for instance.
So I recommend Browns, since they have a tactile bump to prevent mistyping, but are capable of hovering for gaming. They're also not clicky, so are quieter than Blues. I would recommend Clears even more, though, since they are like Browns, but with a bigger bump and stronger spring, but they're quite rare, especially in full size boards. The bump helps to act as a reference point on the upstroke for "hovering" when gaming and the extra tactility is nice when typing.
If you really want a full size board the QuickFire XT is worth a look. Standard layout, removable full size USB cable.
There is a "compromise" board with a keypad, but no arrows and edit keys (you can change the mode of the numpad to become these keys, though) called the QuickFire TK, but it has a non-standard bottom row, so finding replcement keycap sets that fit is almost impossible (especially the 6.5x size spacebar).
The TenKeyLess (TKL) version is called the QuickFire Rapid. This is a very popular board on this site. It's got a standard layout (so you can use almost any aftermarket keycap sets) and is compatible with a lot of aftermarket cases, etc. One of the best value for money mechanical boards out there. They now have a backlit version called the QuickFire Rapid-i, but it costs more.