>>105813407For small powered computer speakers, the iLoud Micro Monitor MTM basically can't be beat. For their size they have impressive bass and overall good sound. You can look up the review from audiosciencereview. But they're quite expensive. iLoud also makes some cheaper models you may want to look up.
If your budget is closer to $50 you're really going to have to hunt for deals, possibly in your local area, to find something decent. I've got some good speakers for very cheap on fb marketplace but it took weeks of looking for what I wanted and being available to get them.
For small speakers that sound pretty good and cost less, I suggest a pair of used Definitive Technology Promonitor 800s. I wouldn't buy a speaker this small at all, but I know someone with a home theater set up with these, and they sound pretty good even at the much further distance than you'd use a computer speaker. They have good clarity and their design suggests they should sound fine up close. They have high quality woofers for the size and can be comfortably crossed over at 90hz -at movie volumes across a loud room-. The downside is you'll need an amp to power them, which can be bulky if you buy something like a cheap used AVR, although that doesnt' necessarily have to go on your desk. Small, questionable quality 20 watt amps are available online for like $20 though.
Look in your local area. They also came bundled with an 8" subwoofer that hits down to the mid-40hz, ask if seller has that too. $20 for a new chinkshit amp or preferably a used stereo or AVR, you can get something several times better for less than twice the cost. if you can't find them locally, I see a pair in rough condition for $65 on ebay. Take off the grills and they'll be ok.
These are bigger than the pebbles but not huge Here are some pics of them on a desk. https://www.avsforum.com/threads/6x-definitive-technology-promonitor-800.3293023/