>>i know i would never want a guy to change who he is just to make me happy... is it the same for guys, are they all looking for the same thing??
I can't speak for other guys; only for myself.
That said, if I wanted to date a fantasy, I'd stick with my h-doujins and never leave the house.
The essence of dating, as I understand it, is that you allow someone else to enter your life and that that someone, reciprocally, allows you into his. For this to happen, there must be mutual trust and mutual honesty.
If you pretend to be someone you aren't simply for the sake of entering into a relationship, the result isn't a complete relationship. You aren't allowing the other person to fully enter your life because you never let him see past the fiction that you've so carefully constructed for him.
But the thing is, even the best actor can't sustain a performance forever. Sooner or later, you'll find that you won't be able to maintain your facade. By that time, if not sooner, the guy you're dating will realize that you've been distancing yourself emotionally from him -- distancing yourself by not letting him see who you really are.
If I were in a relationship and that happened, I'd wonder if my partner really shared my committment to the relationship, or if this wasn't something that she wanted at all. At this point, trust breaks down and the relationship begins to fracture.
You could also encounter other issues: the guy might wonder, "if she can't be truthful to me about who she really is, what else might she be hiding from me?" Deception is corrosive -- once it begins to seep into your relationship, it will eat away at everything it touches.
Granted, the above is an extreme example -- the sort of thing one usually encounters only upon learning that his or her partner is, say of a different sexual orientation than he/she originally professed, or if one finds out that one's partner has committed some serious offense and subsequently lied about it.
With something minor, like (as you noted in your original post) being "intimidating and loud", you might not run into serious problems if you initially covered it up and then subsequently revealed your true self to your boyfriend. Even so, it's better to be honest about that up front. That way, any potential boyfriend will know what he's getting into -- and make no mistake, there are guys out there who like assertive and boistrous women.
In summary, you should only change if you feel that you have a genuine problem that needs to be addressed. But as long as you're of sound health and you remain considerate of others, you should be honest about who you are. That, apparently, is how you'd like your potential boyfriend to be, and mutual honesty is the key to building the sort of trust that leads to healthy and long-lived relationships.