The Vans RV-4 is a great aircraft, simple to maintain, quite economical and very good performance. I've had 3 of them.
They are also not often on the market, so you would need to act quickly (and cautiously) to secure a deal.
As a sailplane pilot, it maybe worth looking for a Fournier RF5. Possibly less availability than the Vans, but combines motor-glider economy with aerobatic capability.
The Jodel D150 Mascaret is nominally aerobatic although most owners seem to respect the aging woodwork and use them just as tourers.
On the lighter side, there's the Rans S10 Sakota which should be well within your budget.
Most of the above should only be considered single seaters for aerobatics sorties. If you want dual aeros, find a partner or two and get an RV-8.