Front Speakers with subwoofer

[robchow]

I have noticed that some front speakers have built-in sub (for example, Polk RTi A7). Most likely than not, these built-in subs are not good at producing lows as dedicated subs from manufacturers such as eD, av123, and SVS. Therefore, purchasing a sub is highly recommended in HT.

So here is my question: if you have a great sub (or dual sub) from one of the aforementioned manufacturers, is having a built-in sub still useful? I am wondering if some money can be saved by purchasing RTi 8 / A5 as oppose to A7.

Thanks