From the details you’ve listed, it sounds like you’re looking for Ralph’s in Worcester. The Middle East in Cambridge has multiple spaces within the venue and is probably in your size range. But speaking personally as someone in the Boston metal scene, I’d always rather go to a show at O’Briens in Allston than the Middle East, though they definitely have a smaller capacity.

Honestly, your number one priority for a party that large in Allston on a Saturday evening should be a place that takes reservations, ESPECIALLY if there are shows that night. If there’s a Roadrunner event, good luck trying to waltz in anywhere in that neighborhood with 10 people.