You can pick a stereo receiver from Accessories 4 Less.http://www.accessories4less.com/make-a-store/item/yamrs300bl/yamaha-r-s300-natural-sound-stereo-receiver/1.html Speaker DIY kit.($260)https://www.parts-express.com/tritrix-mtm-tl-speaker-components-and-cabinet-kit-pair--300-702 Sub-woofer DIY kit. ($230)https://www.parts-express.com/dayton-audio-12-ultimax-subwoofer-and-cabinet-package--300-7096
You would have to list a budget for a pair of speakers and a sub-woofer to be able to give you help you decide. Whatever you find on sale here is going to be about the best deal you can find for new speakers on sale.http://www.techbargains.com/catsearch.cfm/1_7_1 This is about as cheap as you can go for decent speakers and...
Your better off plugging the headphones straight into the FiiO X5. (12-Ohm to 250-Ohms)If the headphones are more then 250-Ohms, then the receiver might be a better choice for driving the headphones.If your looking at a 2.1 speaker setup, then the Denon AVR-2802 should do a fairly good job.
You might be able to find a good price on the Takstar Pro 80 (Gemini HSR-1000) headphones.
Low cost ones usually have a long shipping period.
You could get the USB version, but chances are the motherboard has an optical output.If not, you can always get the Asus Xonar DG sound card, $19 after mail in rebateAs the DG comes with an optical port.