Which Harry Potter house do you think I'd best fit in?

I would say that you sound like a Slytherin to me. You definitely have traits from all the Houses. You threw me off at first because you sounded a lot like a Gryffindor at first with the passion and optimism, transformed in to a Ravenclaw with the studies and fascination with arts, then into a Slytherin, a bit of Hufflepuff because you care and follow your heart.
And dont think of it from a character's view. To be in Slytherin House you quote...
"Slytherins tend to be ambitious, shrewd, cunning, strong leaders, and achievement-oriented. They also have highly developed senses of self-preservation. This means that Slytherins tend to hesitate before acting, so as to weigh all possibilities and what exactly should be done." -wikiapotter
House stereotype and prejudice is what throws people off... Slughorn was a very kind and good person (almost mild mannered, and grandfatherly) and he was in Slytherin; was he not? If anything, Slytherins sound more like leaders than Gryffindors; they always made me feel like the King's right hand man, you know? Very important and could probably take over King duties if they wanted to. And many other Slytherins who, during one point or another, did the right thing. Snape, Regulas, Draco all (no matter how small or big) had good in them.
So take it as a compliment. I myself would put myself in Slytherin because I believe that the House's motto would be "Nothing but your best" And isnt that what all great people expect of themselves?

Judging by your personality, you seem rather outgoing and willing to do whatever it takes to achieve your goals. Major Gryffindor aura there. You're courageous, too, it would seem, and would give up your life for family and friends, if nobody else.
But your interests… the arts, reading, philosophy… only people wanting education and a way in life achievable by knowledge are in Ravenclaw. It would seem like that's what you want.
So which is it, you ask?
Well, if I were a Sorting Hat, I'd put you in Gryffindor :)

I think what house you want to be in influences your sorting the most. I'm sure lots of people are mixture of allot of things. You seem to be very smart and ambitious and hardworking, so it's a little hard to say. I initially thought Gryffondor, but maybe Hufflepuff might suit you more.

I would say Hufflepuff , You hold some quallities that Cedric Diggory and Tonks had and they were in hufflepuff . I do think that is an underestimated house .