Dayne, what size fish are you after and what weight of line are you intending to fish? A 10000 has a more suitable gear ratio for popping and stickbaits but if you want to fish really heavy lines, you may need a 20000 spool. My personal suggestion is to get the right reel and if you need the spools, to get these as an after market accessory. the 10000 spool is a bit small (unless you're fishing PE6) and the 20000 spool is a bit big (unless you want to fish PE10 - 12). For PE8 - 10, you'll find a 16000 spool or a Yumeya 10000D spool ideal.
It appears to me that you're referring to the current model Stellas. The new SW Stellas will be out later in the year so if you're not in a hurry, you might want to consider that as well.
There is minimal weight difference between a 10000 and a 20000. The 10000 spool is supopsed to cast better but I use PE12 on a 20000 spool and it cast really well.