A rough hull speed can be calculated as the square root of the waterline length. If the overall length is 23'', the waterline is probably less than that. Unless your Compac can plane, the hull speed will be less than 5 knots (which would be for a 25'' waterline), but probably more than 4knots.
The theoretical hull speed is determined by the length of the waterline and is typically quoted as the square root of the waterline multiplied by 1.34. Modern monohulls take advantage of the the fact that narrow hulls can push the constant upward so that 1.5 times the square root of the waterline is not that usual.
When you talk about more traditional boats, like the Compac, hull speed really is not all that significant in determining how fast the boat will be. In boats like these, the bigger determinant of how fast a boat is percieved to be, is the percent of time spent at or near hull speed. One of the reasons that more modern designs are as fast as they are is that they spend more of their time at or above hull speed than more traditional boats that need to have a wind in a narrow range inorder to achieve hull speed.
This is a product of a number of factors but the primary three is sail area to weight (the drive to push the boat at speed), stability (which gives you the ability to use the sail area that you have) and ease with which the hull can be pushed through the water.
In absolute terms, while the Compac 23 is a nice little boat, it is a pretty slow boat. In absolute terms they do not have a lot of sail area, stability or an easily driven hull. They are at their best in a narrow range of wind speeds that I would estimate to be 10 to 15 knots. Below that range they lack the sail area and have too much wetted surface to be fast. Above that range, upwind they appear to lack the stability to stand up to their sail plan without generating a lot of drag so they lack the kind of breakaway speed of a more modern performance boat.
Still and all, the need for speed is very subjective and often relates more to where you sail and how you sail rather than some absolute yardstick. On an absolute scale, the Compac 23, with a PHRF of 252, The Compac 23 is faster than a Cape Dory 22, Schock 22 or Catalina 22 but is slower than a Santana 23, C&C 22 or Cal 22.
If you live in an area with predominant winds in the 10 to 12 knots then the Compac should be fine, but if you live in an area like Long Island Sound or the Chesapeake Bay where the predominant summer wind are well below the 10/12 knot range and there are lots of places to go and so a little extra speed means a lot more places to go, then the Compac''s lack of speed could be an issue.