You're bang-on with this. Reverse DNS entries and SPF are critically important. Your forward DNS should also match, eg; if you send from 188.8.131.52, you should have a PTR record for that IP to "mail.mycompany.com" and "mail.mycompany.com" should have an A record that points to 184.108.40.206.
Though as you point out, not all "business class" IP ranges are created equally. Notably, if the ISP allows many other businesses to send spam (from virus infections) in the same range as your IPs, you'll probably eventually be blacklisted as well.
This setup will get you a good outbound setup. I did something similar when I joined the company I'm at now, though took it a step further, and because we have some servers in a data center anyways, I changed our Exchange server to relay it's outbound mail (aka use the stupidly-named "smarthost" thing) to a server running postfix, when then sends to the rest of the internet. The reason I did this was two-fold: I don't really trust our cable co's IPs, and we have a secondary DSL line: if we fail-over to that, I still wanted outbound email to work. This setup allows both, since our mail always comes from an IP in our datacenter netblock. In the 2.5 years we've been using it, we've had no problems with people getting our mail.
The other side of this is inbound: personally, inbound mail on a cable modem hosted in a regular office is a recipe for disaster, eventually. In fact, one of our clients had it happen to them, their office flooded, and their ability to get email was down for several days while they tried to get a new server up and relocate it. Email was actually bouncing back to people sending to them, because nothing was responding. Since their phones were also down at first, it looked like they were out of business, except that they called us to tell us what was going on. You don't want this to happen to your business.
When I first did the email setup described above, I also got an account at dyndns using their Mailhop Forward service. Effectively, you point your MX records at their server, and then they deliver mail via SMTP to your (possibly dynamic) IP. If the office connection goes down, they spool mail for you for up to a week, and deliver it once you come back online. No mail lost, even if your connection is down. In a disaster, you can easily redirect the service to send to another mail server, without having to wait for DNS changes to propagate and all those other servers to retry sending and/or people to manually re-send.
Since then, we got tired of the spam (whatever crappy software we had that integrated with Exchange sucked), and so probably a year ago, we switched to Messagelabs, which provides a similar service to Mailhop but also does virus/spam filtering. Spam went to effectively 0. I HIGHLY recommend using an external company for this.. it costs us a few dollars per person, well worth it, and we don't have to manage anything ourselves. I see Dyndns is now offering something similar as well, I can't vouch for that service specifically but we continue to host our DNS with Dyndns and I have nothing but good things to say about them.