I need a new vacuum as my current one...doesn't suck. I need something that's good for a small (~450 sq. ft.) apartment but I have 2 cats so it has to handle the litter and fur.

I know what you mean with the litter, my old vacuum would turn any straggler pieces of it into dust,lol!  A really good option is the Shark Navigator Upright Vacuum which sells for $175.69!
specifics:
Features:Lightweight (under 15 lbs) amp; easy to maneuver Bagless Infinity Technology traps dust and dirt so the Navigator Never Loses Suction Navigator Power Nozzle provides powerful pet hair removal Super 12apos; Stretch Hose and 30apos; long power cord Accessories includBagless Infinity Technology traps dust and dirt so the Navigator Never Loses SuctionNavigator Power Nozzle provides powerful pet hair removalSuper 12apos; Stretch Hose and 30apos; long power cordAccessories included: Pet Hair Power Brush Crevice tool Dusting brush Cleaning Wand Extra 24" Crevice Tool

Another great option is the Hoover Upright Vacuum which sells for $127.49
specifics:
All vacuum cleaners use suction to pick up surface dirt. Only Hoover's patented WindTunnel™ technology utilizes three distinct air channels to lift and remove the hidden, deep down dirt that other vacuums leave behind.

• Patented WindTunnel™ Technology
• Embedded Dirt Finder™
• 3 Year Warranty
• HEPA Media Bag
• Complete On-Board Tool Kit