Any RAS/quad rail that you install will be up to your tastes your needs and your budget, but you get what you pay for. Just keep in mind your going to add weight up front and change the balance point of the rifle somewhat. There are so many options that you need to take a good look at what you're really wanting from the RAS. Do you want a free float , non free float, one that can take a ton of severe use and abuse , or just something functional and gives that tacti-cool look? If you want something cheap but functional and modular, Magpul's got a good one that is light and nicely adaptable to your own preference. Not a free float but wont break the bank. On the opposite end of the spectrum, I have a Knights armament quad rail (RAS) on my AR and it's built like a tank but also retails for $300 and up. Just sort out what your needs are and work from there. HTH
By the way, what length are we talking about. Carbine , Mid, Full ? Getting you set shouldn't be much of an issue since everyone and their dog is making AR parts these days.