The unofficial amp for the extreme bass club here is the Fiio E12. It is designed to be portable, but I suppose you can use it as a desktop amp as well if you want... Just make sure to charge it up every night. With a typical Li-Ion battery, you want to keep it topped up to prolong the life of it, IIRC. I believe you can also charge the E12 and use it at the same time, but I don't recommend it since you'll likely get a lot of noise in the line and it's not something great for the battery itself.
I get most of my stuff on Amazon. EBay can be unreliable due to lots of fake items or damaged/used stuff marked as new. I would only suggest eBay if you want to save some money and buy used, but make sure you check out the sellers ratings and stuff and the item description.
You can get the E12
HERE. Make sure to avoid the E12A, you want the non "A" version because it is less powerful.
The number of the model is irrelevant to its performance. Higher number does not necessarily mean better. For example, the Fiio E17 is a higher number than the E12, but they are two totally different products that do not do the same thing.
Two of the best pads for the SZ1000 and SZ2000 are the Brainwavz HM5 for comfort and performance, and the pads from the JVC HAM55X or HAM77X. The two JVC headphones are not very good, so I would recommend you not buy them, although, you can buy the pads themselves for much cheaper.
HM5 pads
HERE and 55X pads
HERE. I seriously suggest you get these immediately. These are dirt cheap, even with shipping, there's only a couple still for sale, so definetly get a pair of these ASAP if you are serious about getting a pair of SZ2000's or SZ1000's.
There is also an
"extra thick" version of the HM5 pads,if you want. Here is a comparison of the extra thick and normal HM5 pads...