I've used the MS X4...and found it to be "meh". The GB K8100...is good for a mushroom dome KB. Heres the review I did on it:
Gigabyte Aivia K8100 Gaming Keyboard Review
BUT before you plunk down any money for a mushroom dome kb....try a mechanical. Gigabyte has the new Osmium (I like it). It uses Cherry REDs. I personally love Cherry Reds as they are silent, bump free and OMG
fast. You really want to try out a couple dif types to see what you "like". But quick n dirty is: Blue == Typing. Brown == in between (decent for both games and typing...usually a good choice for first time users. But can be limiting once you KNOW what style you really like). Black == Games. Red == Games ONLY (very easy to actuate wrong key...but great for SPEED).
Some good options are:
GB Osmium
Cooler Master Storm line
Corsair Vengeance line
THEN you get into the more custom KBs like the Daskeyboard and the like. :)