You can improve the flow with a second pump, but not necessarily much can be done about the filtering. With two pumps, I get more time out of the filters, and great flow but the fine particles that drop from the air still fall to the bottom of the pool.
You can't connect the pumps in series, it will not increase flow this way (flow would be the same even if you could). To use two pumps, one has it's hoses draped over the side of the pool, bungees hold them in place and the suction end has to be weighted down else it will rise and suck air. This method does increase water flow in the pool very well.
If you have an extra pump on hand, I'd say go for the double pump setup but if you plan to go buy a new small pump (same as what you have), I'd say don't bother and get something better for a little more $.
I'm not too clear on what kind of better pump/filter would be a better alternative due to the fact that the filters themselves aren't so great. I have plenty of flow with this hokey setup which is about what I'd get if I upgraded to a bigger Intex pump that would have the same filter. If you're only looking to increase flow however, the larger Intex pump will work to do that and then you'll have an extra pump to drape over the side if you want.
The Intex sand filter looks promising, yet it is said that sand filters don't pick up the fines either. I remain undecided on this.
