If you want to hear music with any degree of distinction at wake range you will need at least one pair of HLCDs in an 8-inch variety or larger. Plus, you will not be able to avoid upgrading the power to the tower so add an amplifier to the list also. There is no less expensive way and you cannot replace quality with quantity. Trying to get out on the cheap will only cost you more in the long run. You won't be satisfied and you will have to duplicate the purchase.
Wetsounds is the best quality in a long range projecting tower speaker. You can do an cheap imitation for less with anything. A good option is to purchase a pair of used Wetsounds Pro80s plus an amplifier. You can get this done under $1K. Or, you can get a new pair of Wetsounds Icon8 (8-inch surf speaker) and an amplifier to drive them for in the $1000 area. An automotive 6.5" on the tower is a waste of money. If you are on a budget, wasteful spending is the last thing you can afford.