Go to a dive shop and get plastic coated diving belt weights. They come in various weights, up to about 5 pounds each. A cheap solution for this tweak.
Speaker tweak
I've read that some folks put weights on top of their speakers to help with speaker resonance. I have a pair of Dynaudio 72's. I'm using spikes onto a carpeted floor. Last night, I experimented with setting one brick on top of each speaker. Each speaker was covered with a thin cloth so as not to damage the finish. I don't know if it was my imagination but the sound seemed to tighten up especially in the lower regions. The highs appeared to be slightly more etched but not overly so. The results were significant enough to make me want to experiment with other weights. Does anyone have any suggestions on other weights such as brass that might work. I thought about the Mapleshade heavyhats but I was hoping to find something a bit cheaper while at the same time acceptable in appearance. Thanks in advance for any suggestions.