Try:
http://www.empiretickets.com/
I have used them in the past (in Atlanta) with great success. In the end you pay a much higher price, but, you have a chance to get a seat in the first 20 rows. There are a few other on-line ticket brokers, but, since I have used Empire I will recommend them.
Almost all Sports Clubs in the states (and Concerts, Plays, etc.) use
http://www.ticketmaster.com/. I have used them also. Unlike Empire you will get seats at "Face Value". They will show you the Best Seat Available (based on how much you want to spend). Unlike Empire I would strongly doubt you would ever get near the first 20 rows. Ticketmaster also slams you with a bunch of junk fee's that fringe on robbery. NOTE: Still, the ticket prices are lower then Empire.
My rule of thumb is this: If I am buying an event where I know a bunch of seats will be available I use Ticketmaster. If it is a tougher ticket and I want up close or know it is the only way to see the event I use Empire.
I do not know much about the Magic and how well they draw - but - you may want to consult both sites and make a decision.
Seat Reselling (or Scalping as we call it) is illegal in all US States other then Ohio. So, I have never understood how Empire does it - but - they must have found a loophole somewhere! And, they advertise on many radio stations - and since I (and many friends) have used them multiple times with absolutely zero problems I am willing to go out and say you will have no problems. By my definition they are Scalpers and illegal - but - they have been out there a long time and no one has stopped them. So, I can only think they have some agreement with the Franchise I am unaware of.
If you want to watch real Basketball I would suggest driving to Miami to see Shaq and the Heat - as the only real basketball you will see in Orlando will be from the visiting team! I would also tell you that better Basketball can be found at the University of Florida (in Gainesville about 2 hours north). While they start the season in November college teams usually play bums until Jan 1. Then, the conference season starts with conference play (and UF is in a Fantastic conference).
As for football, the TB Bucs have had a dismal season (0-3) and are going no where! Tickets for them should be plentiful at this point! The draw in Tampa is truly the Stadium - which is fantastic! The Miami Dolphins are also looking like imposters!
The Jacksonville Jaguars, on the other hand, are the best Pro Football team going in FLA. But, they have a loyal following and are sold out (you would have to get tickets on Empire).
Bang for the Buck I would suggest you think about a Hockey Game. Tampa has a fantastic team and is about 1.5 hours from WDW. And, believe it or not, Hockey may be the best "Fan Friendly" sport in the US. I took two Brits to a game last year (who had never seen hockey) and they went ahead and bought tickets for a game 3 nights later!
Lastly, University of Central Florida (UCF) plays in Orlando and is in a "semi" big time conference. They have a great football coach and probably put on a cheap and entertaining show!. In fact, it is probably the best thing going in Orlando! Most likely you can just walk up and buy those tickets. Cannot give any reccomendations on UCF Basketball!
Lastly, at many US Pro Event their are Scalpers. These guys will be holding a sign that says: "I need Tickets". In the end, they will be reselling tickets. Is it illegal? Yes! Do the police intercede - once in a Blue Moon. I have scalped many a ticket with no problem.
But, you need to be carefull with Scalpers! They will have you give them the Money and then give you a bogus ticket or will take your money, hide some of it quickly and then say "Hey, you only gave me half!". And, when this happens no Cop is going to come to your rescue!
A rule of thumb is to stay away if they are in a group (3 or more). You also should have a Seating Chart to see exactly where your seat will be! A better policy, unless you are experienced with these folks, is to just stay away.
I am a Yank, but, have worked in Leicester for most of the year. Thus, I peruse the UK board. I am also a Sports Nut (I even follow Cricket!) and can give you my opinions on prices, etc. If you need more assistance please do not hesitate to PM me.
That should tell you everything you need to Know about Florida Sporting events and how to obtain tickets!
Have fun!