MSI 64MB Ti4200
The best value I know of is the MSI 64MB Ti4200. These cards doen't cost a lot but do deliver. They have very consistant ability to run 300/600MHz at a nice price.
If you have your heart set on a 128MB card, I recommend finding the cheapest Ti4400 you can get. The slow ram on the 128MB Ti4200's means that overclocking is a real hit or miss affair, with few allowing more than 550MHz on the ram. I went with an Abit Ti4400, and even though I have probably the worst example in exsistance it runs the 300/650MHz Ti4600 default. Very few 128MB Ti4200's will reach this level, and the ones that have a shot at it cost as much as a Ti4400.