Upgrade monitors or add a sub?

Howdy friends!

For the last 6 or 7 years I've been mixing on "meh"-quality Samson 65a, 6.5" monitors. I *guess* I've gotten to know them, and they've served their purpose until now.

Over the last few years, my priorities have shifted from tracking and mixing live audio to producing a lot of bass-heavy electronic music (sample). 

My current dilemna is, should I upgrade my monitors, or add a sub? In terms of monitors, I've had my eyes on Rokit 8s, which I love the sound of over the other comparably-priced monitors that I've heard at my local Guitar Center, including Behringers, Mackies, and a few others. They have pretty good bass response, but I'm worried that it just might not be enough. In terms of subs, I've had my eye on the 12s, also by KRK. It's a 12" sub with solid, deep response. 

I'm leaning more towards adding the sub, then in a year or so upgrading the monitors, but I'm not completely sold on the idea. Any thoughts from you guys?


edit: Google Chrome marked "dilemna" as misspelled. I could have sworn that I spelled it correctly, so I googled it. Turns out it's rather controversial! Anyway...

A sub would be the less-expensive choice for now, allowing you to defer replacing the Samsons until your lottery investments start paying off. Subs can be pricey too, but M-Audio makes one (BX-10-something) for $450 that'll do the job just fine. I've had one for several years now with no problems.

Personally, I often wish I'd just gone with larger woofers and foregone the sub. It would have simplified things. Most nearfields with 8" woofers don't really need a sub, since you don't really need to hear down to 20Hz. If your speakers are reliable to 40Hz you're good - just filter out everything lower than that and save yourself a lot of headaches. My speakers have 7.25" woofers and fall just short of having enough bass extension to not need a sub.