Protein,Muscle,Chubby Cheeks?

Hi all,

I’m trying to gain muscle/strength and am considering protein powder to up my protein intake significantly so I can get the most from my workouts.

I work out four times a week => upper/lower/upper/lower and am a relative beginner.

I’m 173lbs and bit less than 6’ so i figure about 120grams a day (given I’d expect I should quite easily make up the rest in regular diet).

My only hesitation is that I’ve seen two individuals who took lots of protein, and whilst they worked out and saw strength gains, they became chubby and appeared to gain a lot of fat. One of them regretted the chubby/strength trade-off, the other didnt. Whilst I don’t know the specifics of their diets, so can’t guess as to where precisely these guys went wrong, I have two questions about buying protein powder:

1)What is the most likely cause of large fat gains on high protein diets? One of the aforementioned individuals suggested it was because his protein powder was not the low-carb variety…
2)What are some of the differences worth noting when choosing between low-carb protein powder and ‘ordinary’ protein powder.

I’d go for the low carb grow formula right here, but shipping is a bit of an issue for me…anyway, any help appreciated.