Btodde, you sound like an ectomorph...how's your metabolism? When you get older you may have to be concerned with fat as your metabolism slows down, but based on what you wrote about yourself, I doubt that's a problem with you right now.
In fact, you sound pretty similar to me. I was 125 lbs at 22 years old when I started lifting and having already stopped growing as an adult. I'm a hard gainer and now 7 years later I weigh 165 lbs, and would weigh more had I not been so stupid to ignore my legs until last year -- my upper body is well developed but my legs are catching up now. I can lift heavy weights compared to guys who outclass me by 50 lbs, and definately more lb for lb in most cases.
If I were you, I'd ignore concerns about fat. You're still young enough to do that. Bulk up first, then worry about cutting if you have to later on. I bet you're one of those types like me who can eat a can of crisco and not gain an ounce! I wouldn't do much cardio...just enough for keeping your endurance up, but not enough to start burning muscle fiber for energy. If you're an ecto, you probably don't have much in fat stores for energy. Eat constantly, supplement with creatine and various protein drinks/powders. Mix a protein drink before you go to bed and keep it by the bed. If you wake up for any reason down it...8 hours of sleep is like fasting for people with fast metabolisms! If you always sleep through the night, set an alarm in the middle of your rest...as for me, my body wakes me after 3.5 hours for protein intake.
You sound like you're making great gains...225 lbs at 130 lb bodyweight is very good. That's 1.73 times your bodyweight! Consider a 200 lb man who pushes a comparable 346 lbs! I know many who cannot do that. Are you lifting 225 for reps or max? In any case, if you hit a plateau mix up your routine...add different exercises, change the order you do your routine, and/or increase intensity. Always life heavy with relatively low reps. Aim for twice your bodyweight in strength on the bench for a goal.
Good luck, I know what it's like to be a hard gainer. But guys like you and me sometimes have an advantage in looking striated and cut at all times. Any mass you gain really shows.