This is fairly simple - GET A LIPO! LiPo's (Lithium Polymer batteries) are the best option for any RC'er. We strongly recommend getting a LiPo battery if you want to get the most out of your SC10. Lipo batteries provide more power, have a longer life, weigh less, and give you LONGER RUNTIMES.
Longer runtimes are the biggest advantage of LiPo batteries. One of the major knocks of electric RC is that you spend all this time fixing your vehicle and charging the batteries and then you only get to run your truck for 10 minutes. This is not true anymore. LiPo's now give you the option of running your truck for a solid 20-30 minutes (or more) with no detectable decrease in power before cutting off.
Yes, LiPo's do cost more but we think it is well worth the money. A good starter LiPo battery is the Team Orion 2s 7.4v 25c 3000mAH Rocket Pack - $48.95 The 25c rating is your discharge rate - a higher c will give you more punch. The 3000mAH affects your runtime - higher mAH, longer runtime. This battery should give you a solid 15 minutes of quality runtime.
The battery we recommend, if you have the cash, is the Dynamite 7.4v 6000 mAH 2s 25C LiPo. This battery has the same C rating (same punch as the Orion) but has a much higher mAH (6000mAH>3000mAH) giving you much longer runtimes. Expect the dynamite battery to give you a solid 25-30 minutes of runtime. The Deans connectors are also a must. Old-school white battery connectors do not maximize the output of your battery and will cost you punch. The Deans connectors are much more efficient and they are also easier to connect. Remember, your ESC must have Deans connectors to use batteries that have Deans connectors (go to your LHS if you need help).
If you want to go BIGGER, try a battery with a higher C rating (30-40C) or higher mAH (6000 - 8000mAH). These batteries will cost you upwards of $150.
Team Orion 2s 7.4v 25c 3000mAH Rocket Pack - $48.95
Dynamite 7.4v 6000 mAH 2s 25C LiPo
Chargers
There is one brand of chargers that has proven to be a great low-cost charger for LiPo packs. This is the Dynamite Passport AC/DC LiPo 6S - $64.99. You can plug it into the wall, or you can use your car battery to power it. It also has a cell balancer built right into the charger (this ensures that each cell in your LiPo pack is charged evenly). The charger is easy to use and only runs about $65. This charger only works with LiPo's, so if you still want to charge your Nickel-Metal battery packs, you'll need another option.
Dynamite Passport AC/DC LiPo 6S - $64.99
Recap: Get a LiPo battery. They will last much longer and they will provide much more runtime. It's pretty simple. You get what you pay for and LiPo's are worth the extra cash.
Estimated Costs for battery and charger: $113.94 - $154.98