Welcome!
And welcome to the world of being owned by a rat.
It sounds like you've got some issues developing with your little guy though. They can still be worked through, but you don't want to rush through things or make changes without a little education first.
Your sweetheart has become cage aggressive. It will require patience and careful work to help him overcome this. Also, yes, he does need a rat friend in order to be happy and well balanced, but you will want to learn how to do proper introductions and before you get a new rat. Males can be very territorial depending on their age and temperament, and you won't be able to buy a new rat and just put him in Louigi's cage safely. Since it sounds like Louigi already has a potential temperament or fear issue, you'll want to proceed that much more patiently and carefully.
I found a few articles for you to read and some sites that might help if you're willing to work.
First of all a little 101 on aggression and causes:
General introductory article to new rat owners:
http://www.associatedcontent.com/article/5638280/how_to_tame_your_aggressive_pet_rat_pg2.html?cat=53
Another introductory article on rats that bite:
http://www.fancy-rats.co.uk/information/guides.php?subject=ratsthatbite
Next, what can you do about the biting?:
Step by Step training Shy or Biting Rats:
http://www.sandyscrittercity.com/trainingshyorbitingrats.htm
http://www.fancy-rats.co.uk/information/guides.php?subject=ratsthatbite
Outstanding site you can search and find video instructional training of fearful rats, biting rats, and videos on how to safely introduce two rats together (along with a plethora of other great care videos):
http://www.joinrats.com/
Top mistakes of new rat owners and other new rat owner questions answered. Also a bunch of care questions answered w/ intros and trust training:
http://www.fancypetrats.com/pet-rat-information.php (Scroll down to find links)
If you'd like a first hand account of experience introducing male rats to each other, I've got a thread here that walked through an entire month of me obtaining, bringing home, and trying to introduce and integrate my six boy rats with each other. I was successful in the end, so hopefully something in the thread will be helpful to you too:
http://www.paw-talk.net/forums/f16/ggmr-naked-58068.html?highlight=alabama+ghost+boys