Thats a big question, but in a nutshell, and IMHO, depends upon you, your body type and the program you are on. But I believe that you can get bigger, with out lifting so heavy that you would need a spotter, yes. You can lift heavey, lower reps, and keep the weight in CONTROL, and increase when you are physically able to handle it by yourself. Intensity is important.
Some people like to have a spotter, so they can squeeze out the last drop, or go to failure but I really believe this is a flase sense of security because if your technique goes to crap, you risk injury and usually when your attempting to get every last ounce out of yourself, your technique goes first, and other non targeted muscle groups take over or something gives out, like your back, knee, shoulder etc. A spotter will not always catch you/it in time for that not to happen. You REALLLYYYYYY have to trust your spotter. Changing to a bulking diet is going to have a huge impact as well.