Nearly everyone can have 60% gain the first 18 weeks of training, even if they train badly.
Power lifting (low reps) will make you stronger, but, size is a function more of local muscular endurance. Look at a power lifter. Strong as heck, but, not as big as say a speed skater, or a cyclist, or a football player, or a bodybuilder. Moderate reps on legs, you'll find, will be best for size.
To enhance your strength, low rep work is o.k from time to time (read up on periodization), but, low rep work will also risks injury. It's best, especially if you're a neophyte, to leave the low reps alone, and to develop your anaerobic threshold, and vascularization, early on to give you a support structure and to lower your chance of injury.
Doing low reps early on is a great way to compromise form, and end up injured. Probably not the wisest idea right now.