At this point the square drivers are pure BS. While the idea of moving weight to the corners to raise MOI has some merit they have not gotten the execution right yet. They're selling all sizzle and no steak. The odd shaped driver like the Sumo². FT-i and Hibore might someday offer some sort of benefit over conventional shapes, but right now they don't. They're not longer, they're not straighter, they're not more forgiving, they're not better in any measurable way. There's nothing so wrong with the 400cc R7 that a newer driver would be a big improvement. If you want to spend some money on getting better there are two things to do:
1) Lessons
2) Get on a launch monitor and get fit. You would have FAR more success and FAR better results by optimizing your launch conditions than you would by just blindly buying a new geometry driver.
You can't learn jack by heading out to a shop and whacking a few range balls into a net that's 10 feet away. You have to get fit by a professional with a monitor, buying a club just because you saw an ad about it is just as likely to make you worse instead of better.