For that budget you really won't get much of a tub at all with either Hot Springs nor the Dimension One's. However, you can get a pretty decent sized tub from Sundance's parent company's Spas, Jacuzzi. I think you could pick up a J365 or possibly even a 400-series tub. I am not a dealer but do own a 7 year old J375 that has been VERY economical to operate and I paid only $6,500 for mine with stereo included. If was a few years back and although prices have gone up, the recent poor economy has also held down such increases over the past 3 or 4 years so the smaller 365 should be easily obtained for your target price.
However, the MOST important part is how the jets feel to YOU so try out different models until you find something you like.