You may not feel much but your abdominal fat will start to disappear rather quickly...Because they imitate the signals your pituitary gland sends to your gonads. The gonads increase the amount of test as a result. Unless you're hypogonadal in the first place, you're not going to feel much even going from 500 to 900.
Within "normal range" lower levels are associated with significantly higher abdominal fat but no difference in muscle mass. A study was done where they found men with T levels at 300 versus men with levels at 600 has almost 40% more abdominal fat. The higher your level within that range, the lower your abdominal fat will be due to T making fat cells more insulin resistant but making muscle cells more insulin sensitive, or selectively enhancing and prioritizing the body's uptake of glucose into muscle cells instead of fat cells.