Taking a planet with low-tech?

[serpwidgets]

I'm on turn 24 and there's a neutral race in the next system. I've wiped out everything of theirs except their home planet, and I want to try to either make them surrender, or wipe them out. I'm playing with strategic combat only cuz I want to learn how to make the best of what it does with that in multiplayer.

I have 5 destroyers and 6 frigates, and their home planet has 8 weap platforms with 3 cap ship missile I's each, and 20 satellites with Du II. I've tried all kinds of stuff, including putting all missiles on my ships and setting the fleet to max weapons range, but they still end up getting killed by the planet's missiles and really don't do any significant damage to the planet or the satellites. Is there a way--without researching a ton of new tech, I've got it on high cost for tech and ~14K research points--to take this planet?

Also, will blockading it do any good?