Do you wanna build an amplifier? Sure, there are probably a lot of cheaper options out there, but I bet none would as good as the pure class A Amp Camp Amp from diyaudiostore.com. Designed by Nelson Pass of Pass Labs and First Watt, not only was it really easy to build with an A-Z guide and youtube vid available, but also really quite satisfying to hear the fruits of your labor. 8w @8ohms is not a lot, but all of these are quality watts and puts some of my more expensive amps to shame. Compared to Schiit Aegir in the review, but really, it's the DIY portion that matters the most. If you want to get a feel of how amps work, this is the best way to start.

Link to Sound Demos:
Sound Demo 022 Amp Camp Amp    • Sound Demo v2 022 Nelson Pass Amp Cam...  
Sound Demo 015 Schiit Aegir    • Sound Demo v2 015 KEF LS50 Schiit Aeg...