For fun, I asked Claude (4.5 Sonnett) your question:
Final Design Summary
| Parameter | Spec |
|---|
| Drivers | 2× Eminence CB3010N-8 |
| Wiring | Parallel = 4Ω |
| Power handling | 900W program |
| Box volume | ~26.6L gross internal |
| Tuning | ~66Hz |
| Ports | Two 2" diameter × 3" long |
| -3dB low | ~62Hz |
| High end | 3kHz+ (per driver spec, usable to 3.4kHz) |
| Sensitivity | ~97dB/1W/1m |
| Max SPL | ~120dB real world |
| Cabinet size | 17" W × 14" H × 11" D |
| Est. weight | ~28-30 lbs |
| Construction | 1/2" Baltic Birch, internal bracing |
A 212 Neo cab, 28-30 lbs, hitting 120dB, tuned to 62Hz. Fits your amp, fits your five-string, fits in the back seat of most cars. The CB3010N-8 at 94dB sensitivity is actually slightly more efficient than most comparable drivers in this class, and two of them in a well-tuned small vented box is a very strong answer to your requirements.
The one caveat — at the box volume per driver I've calculated (~13L each), you're running on the lean side of optimal for this driver. WinISD would let you fine-tune whether a slightly larger box (say 30L total) gives meaningfully better low-end extension or whether the current numbers are the right tradeoff for the size constraint. Worth the 20 minutes to model it before cutting wood.