Parasound's Zamp is more expensive - $300 - but a used one could fit your budget. It doesn't offer as much power, but it's been a very popular small amp over the years. And while we're talking about less power (albeit likely still enough to handle patio/backyard speakers), there's always Sonic Impact's T-Amp (available here and here , among other sources) - it's only 10W or so and you'll want to pick up an AC adapter (unless you already have one handy), but for $30 it's an entertaining option.