Amp Stands--- How high? ----Sandbox??

I just bought new (2me)monos,tubed jobs ( CJ8's.) In the first place my old stands are to small. The old stands are the Solidsteels. They are 7 and 1/2 in. high. (Platform t carpet) The price on some stands can get pretty high,esp. when you need about 20x20,in size. Ok,I just don't know. Is "how high" important? Then we get to a budget possibility. Being slightly handy,I could make some of those "bright Star" clones. Are they a decent alternative,and then back to "how high"? If it's not detrimental I would like to go "lower". Thank for any help,guys.
I have my amp on a sand filled box 12" off the floor. I found that lower than 12" my amp was always filled with dust from the carpet. As far as the sand filled box, it made no difference in isolating shock from the floor and I still had to put rubber squares under the stand for isolating floor vibrations. I think the weight of the amp settled the sand and it compacted to a firm base. I have had very good results with a sand filled base on my transport.
Conrad Johnson premier 8 amplifiers benefited from a 4 inch deep bright star clone sand box in my previous system made everything a little clearer and didn't slow the bass response like I thought it might.
Thanks for the input so far. I should have mentioned why I would like to go lower with the amps. There is a center ch. speaker--on a stand behind the amps---Can't raise that, then you have a problem with the speaker being in the way of the bottom of the screen.-- Same as the amp obstructing the speaker. Thanks
If you want to go cheap, pick up some one inch MDF and cut to size then add three or four cones, pick some granite paint up and paint. I use to use the sand boxes
and I felt they dulled the sound of my system! so I use the lovan stands with maple patforms, iso blocks and triple point cones and they work much better than the sand boxes! Happy Listening!